Good evening! What a huge match we have for you this evening as the World Cup qualifying campaign comes to a close in Group D with everything still up for grabs.

Wales host Republic of Ireland at the Cardiff City Stadium tonight in a match that could see either side win the group, finish second or miss out on the playoffs entirely, so it really is all to play for here.

The exact permutations are very complicated - particularly on the part of Wales - and I will take you through them a little later, but for now let's start with a look at the team news...

WALES STARTING XI: Hennessey; Gunter, A Williams, Chester, Davies; Allen, Ledley, Ramsey, King, Lawrence; Robson-Kanu

WALES SUBS: Maxwell, Ward, Ampadu, Lockyer, Taylor, Edwards, J Williams, Brooks, Woodburn, Hedges, Vokes, Bradshaw

IRELAND STARTING XI: Randolph; Ward, Clark, Duffy, Christie; Brady, Hendrick, Meyler, Arter; McClean; Murphy

IRELAND SUBS: Doyle, Elliot, O'Shea, Keogh, Whelan, McGeady, Hogan, O'Dowda, Hoolahan, Hourihane, Maguire, K Long

What can we make of those two sides, then?

Well, no matter how long we have known for, the glaring omission from the Welsh starting lineup is that of Gareth Bale, who remains sidelined with a calf injury which has also left him as a doubt for Real Madrid's Champions League double-header against former club Tottenham Hotspur later this month. Bale's importance to Wales cannot be overstated, but they picked up a good win in Georgia without their talisman on Friday and will be hopeful of doing the same again tonight.

Bale has so often been the hero for Wales in recent years, but in his absence on Friday it was Tom Lawrence who stepped up to the plate in some style.

The midfielder scored the only goal of the game in Georgia, and it was some strike too. Aside from being a good goal, it could prove to be a hugely important one too, keeping Wales in control of their own fate heading into tonight's match. Lawrence is rewarded with another start this evening.

Aaron Ramsey is arguably the star man in the absence of Bale and, having made his 50th appearance for Wales on Friday, the Arsenal midfielder is named in the starting lineup once again tonight.

Ramsey is the highest goalscorer in the current Wales squad with 13 to his name - the only player to be in double figures for the Dragons from those at Coleman's disposal tonight. Vokes in the next highest with eight goals at international level, although he misses out this evening in favour of Hal Robson-Kanu.

Robson-Kanu's return is the only change made by Chris Coleman to the team that won in Georgia, with Vokes having to make do with a place on the bench this evening.

That means an unchanged backline of Davies, Chester, captain Ashley Williams and Gunter, the latter of whom is the most capped player in the current Wales squad with 82. Williams is not far behind, though, and tonight will make his 75th Wales appearance.

While Wales are without Bale, Ireland are also missing some key players for tonight's crucial fixture - including Seamus Coleman, who suffered his horrific broken leg after a challenge from Neil Taylor in the reverse fixture of this tie.

Shane Long was also ruled out of the game this morning, which is a big blow for the visitors considering he is the only player in double figures for goals from the current squad. His tally of 17 leads the way since Robbie Keane hung his boots up following an incredible international career.

Daryl Murphy will lead the line in the absence of Long, and the striker has an impressive record so far in qualifying.

Murphy has averaged a goal every 55 minutes during the campaign so far, netting three times in 166 minutes for his country - including twice on Friday to fire Ireland past Moldova. Both of those goals came in the opening 20 minutes in Dublin, and both Ireland and Murphy will be hopeful of another quick start this evening.

Martin O'Neill has made three changes to his side from that win over Moldova, including returns for both James McClean - who is the highest-scoring international in Ireland's side tonight with nine goals to his name - and Robbie Brady.

The midfield pair missed the win over Moldova through suspension, but return to the starting XI this evening alongside Bournemouth's Harry Arter. Hoolahan, Long and O'Dowda are the men to drop out for the visitors.

Interesting for such a big game, Martin O'Neill has decided against bringing his two most experienced players back into the side tonight.

John O'Shea and Aiden McGeady both have to make do with starting from the bench this evening, despite boasting 219 caps between them, although they could be useful substitutions should Ireland find themselves needing to manage this game.

Right - let's get down to explaining the mess these sides find themselves in this evening, as it gets very complicated very quickly.

Wales are currently in the driving seat out of these two teams in Group D, leading Ireland by one point heading into tonight's match. Serbia are a further one point ahead of Wales, meaning that automatic qualification is in their hands this evening as they host Georgia. Serbia will be expected to win that match, but any slip-up would open the door for either Wales or Ireland to win the group and seal their place in next summer's World Cup.

The simplest scenario for either side tonight is to win. Victory would guarantee them a place in the World Cup qualifying playoffs at least, while it could be enough for them to win the group if Serbia fail to beat Georgia following the group leaders' 3-2 loss in Austria on Friday.

Should Wales win and Serbia draw then Wales would go through as group winners, but should Wales draw then they would need Serbia to lose by two or more goals to ensure they qualify automatically.

A draw tonight would guarantee at least second place for Wales, which is the most likely scenario should a stalemate happen as Serbia are not expected to lose at home to Georgia, yet alone by two or more goals.

This is where it begins to get complicated, though, as even though Wales are likely to finish second with a draw, it still may not be enough to guarantee them a place in the playoffs. There are only eight playoff places available from the nine groups, and Welsh fans will have their eyes peeled on Ukraine's match against Croatia in Group I too as that match will also have an impact on the hopes of tonight's hosts.

A draw for Wales tonight will only be enough to see them clinch a playoff place if Croatia also draw in Ukraine while scoring the same number of goals as Wales, for example both matches finishing 1-1.

A victory for either Ukraine or Croatia coupled with a Wales draw will almost certainly see Chris Coleman's side miss out on a place in the playoffs, while should Croatia and Wales both draw but Croatia score more goals in their draw - such as a 2-2 and a 1-1 - then remarkable it would come down to fair play, which Croatia are currently winning.

What that means is that not only is the result vitally important for Wales tonight, but even things like yellow and red cards could come into the equation. Seven of Wales' squad are one booking away from a suspension which would see them miss the first leg of the playoffs if they get there, and that could prove to be enough to prevent them from reaching it at all.

For Ireland, things are a lot more simple. Their only choice is to win, which would guarantee them at least a playoff place and could be enough for top spot if Serbia fail to beat Georgia at home - although even a draw for Serbia would leave Ireland needing to win by five goals here.

Got all of that? Good - because there is a chance that the fate of Wales may not even be decided until tomorrow too.

This is the least likely of the two options, but unless Wales lose tonight then they will not know for certain until tomorrow whether they are definitely out or not. Missing out to either Ukraine or Croatia tonight would leave Wales needing lowly Gibraltar to get something from their trip to Greece tomorrow, and for Bosnia to beat Estonia and overtake Greece as the worst runners-up. A very unlikely scenario.

To summarise, then - the permutations for tonight's match are as follows:

Wales win: Wales are guaranteed at least a playoff place, and would win the group if Serbia fail to beat Georgia.

Draw: Wales would need a draw between Ukraine and Croatia in Group I, in addition to scoring the same number or more goals than both of those teams, to reach the playoffs.

Ireland win: Ireland leapfrog Wales and finish at least second, guaranteeing a playoff place in the process.

I told you it was complicated! So how much chance to either side have to get what they need tonight, then?

Well, Wales are one of only six remaining teams yet to lose in the whole of the European section of qualifying and come into this match on the back of three straight wins having drawn five in a row before that.

Another victory for Chris Coleman's side tonight would make it four on the bounce for the first time since a run of six under Mike England in 1981.

Wales' unbeaten record in the current qualifying campaign means that they have not lost since their semi-final exit from Euro 2016 last summer, which was just their second major tournament in their history.

To put into context what they could achieve tonight - and what they achieved in France last summer - Wales have only ever reached one World Cup before, in 1958, and even that was as a result of some political and footballing irregularities which gave Wales a second chance.

That 1958 team included the likes of Ivor Allchurch, Cliff Jones and the great John Charles, which is the company this latest golden generation - as Coleman has dubbed them - could be keeping with a win tonight.

Wales are unbeaten in their last five home matches stretching back to a 3-2 defeat at the hands of Netherlands in November 2015, although they have not won back-to-back games in front of their own fans since June of that year - tonight would be a perfect time to do that!

Wales' unbeaten run at home in competitive matches goes back to September 2013, though, winning six, drawing four and keeping seven clean sheets in their 10 such matches since a 3-0 defeat to Serbia.

That defeat at the hands of Serbia was also the last time Wales were beaten in World Cup qualifying - a run which is now 11 matches following their crucial and impressive victory in Georgia on Friday.

That triumph was their first away in a qualifying game without Bale since 2009, when they beat Azerbaijan 2009, and they will need to produce another good performance without their talisman tonight.

Ireland must win this match as well, but they have emerged victorious in just one of their last four outings - a major dip in form which has left them in this unenviable position on the final matchday.

Martin O'Neill's side began qualifying so well, with 10 points from the first 12 on offer, but they then took just three points from the next 12 to slip behind Serbia and Wales in the race for a top-two place.

Friday's win over Moldova ended their three-match winless streak, which included a really damaging home defeat to Serbia last month, but their form over the whole year has been questionable.

Ireland have won just two of their eight matches across all competitions in 2017, and tonight are looking for consecutive wins for the first time since November of last year. They are, however, unbeaten in their four away games during the current qualifying campaign, winning two and drawing two.

Ireland have not won on the road so far this calendar year, though, losing to Mexico in a friendly and drawing in Georgia - another result which looks like it could come back to haunt Ireland.

Whatever happens tonight, though, Martin O'Neill will remain in charge for the foreseeable future having last week put pen to paper on a new two-year deal which carries him to the end of Euro 2020.

PREDICTION: We're 10 minutes away from kickoff at the Cardiff City Stadium, which means that it is time for a prediction!

This is such a tough one to call tonight. The two sides are evenly matched and both missing arguably their best players, while both teams could well need a victory to keep their World Cup hopes alive. It is set up very nicely for the neutral and really could go either way. In usual circumstances with so little to separate the teams I would plump for a draw, but these are far from usual circumstances and there should be a winner this evening simply because both teams need one.

Sports Mole says: Wales 2-1 Ireland

Even history suggests that there will be nothing to separate the two nations today, with their head-to-head record being exactly even at five wins apiece and four draws.

The crucial difference which may lean things in Ireland's favour, however, is that Wales have never beaten their Celtic rivals in a competitive contest. They have twice draw in such circumstances - in 2007 and the reverse fixture of this campaign - but they have also lost twice, with Ireland winning out 1-o winners in another 2007 contest and 3-0 victors in 2011.

That 3-0 win from 2011 is actually the last time either of these two sides scored against each other, with the past two meetings both ending goalless.

The most recent of those came in Dublin in March when they played out a stalemate in the reverse fixture of this one, while they also drew 0-0 in an August 2013 friendly at this very stadium.

Wales have actually failed to score in five of their last six matches against Ireland, with a Jason Koumas brace in that 2-2 draw in 2007 being the only exception during that run.

Indeed, Wales' recent record against Ireland is poor despite the even nature of the all-time head to head. Ireland are unbeaten in their last seven meetings stretching back to February 1992, while they have only lost one of their last 10.

The Welsh anthem - by the request of the players - stops after a few bars to allow the fans to sing at their own tempo, and boy to they belt it out. Incredible stuff. We're very close to kickoff now, so before we get started let's have a reminder of the team news...

WALES STARTING XI: Hennessey; Gunter, A Williams, Chester, Davies; Allen, Ledley, Ramsey, King, Lawrence; Robson-Kanu

IRELAND STARTING XI: Randolph; Ward, Clark, Duffy, Christie; Brady, Hendrick, Meyler, Arter; McClean; Murphy

KICKOFF: If that anthem and this atmosphere doesn't inspire Wales, nothing will. Ireland get us underway amid a Cardiff cacophony of noise.

The first big roar of the game greets an early corner for Wales, who have begun this match more confidently than Ireland.

CHANCE! Half a chance for Wales from that corner as Robson-Kanu gets across his man to meet Ledley's delivery, but he cannot steer his header on target.

UPDATE: No goals from elsewhere in Europe just yet, but I will keep you up to date with any major goings on as and when they happen - with a particularly close eye on the Serbia and Croatia matches.

Chris Coleman will be happy with his side's start to this match. They have controlled possession so far and are not looking to just sit back and cruise in this match. They have already shown attacking intent tonight and know that only a win will leave no doubt over their chance of reaching at least the playoffs.

OFF THE BAR! Allen is tripped in midfield and looks to the referee for a free kick, but Damir Skomina plays a good advantage as Ramsey collects the loose ball. He unleashes a vicious drive from range which Randolph gets a fingertip to to help it hit the top of the crossbar.

Ireland have not got going in this opening 10 minutes. If you didn't know which team needed to win so far, you'd say it was Wales rather than the visitors.

Wales are camped inside the Ireland half at the moment. The visitors just cannot get out and Murphy has barely had a kick so far.

Wales win another corner, but this one swings straight into the arms of Randolph. It is all very tense inside the Cardiff City Stadium at the moment.

YELLOW CARD! The first card of the day goes to Allen, who swings for the ball but just misses out to Meyler, who bears the brunt of the challenge.

The initial delivery from Brady is well defended by Williams, who is called into action again seconds later to put McClean's fizzing low ball behind for a corner.

Almost a chance from that corner as McClean finds a bit of space inside the box, but the ball skims up too quickly to him and it is a swing and a miss. Hendrick does get his shot away, but it flies well over the crossbar.

SHOT! The ball breaks to Allen 25 yards from goal, but Clark is alert to the danger and does just enough with his challenge to ensure that the midfielder cannot hit the target.

This is a real tussle at the moment. It is scrappy, and not particularly great in terms of quality, but it is full-blooded as you would expect from these two teams.

CHANCE! Ireland have their first chance of the contest as Wales make a mess of dealing with a long throw-in into the box. The ball breaks to Hendrick, but he cannot connect properly with his shot and Wales eventually scramble it clear.

SAVE! Lawrence was the hero on Friday and he tries his luck from range again here following a neat turn in midfield. His effort bounces in front of Randolph, but it is easy enough for the keeper to collect.

UPDATE: If you're wondering about the lack of updates from elsewhere... it is because nothing is happening elsewhere. Still no goals in any of the nine matches across Europe tonight, although that is fine by Wales as, as things stand, they will be in the playoffs.

Robson-Kanu has been lively for Wales so far tonight. There may have been a few eyebrows raised when he was selected ahead of Vokes tonight, but he certainly gives them more industry up front than his Burnley compatriot.

SHOT! Ireland have caused a couple of problems through their few set pieces so far. Here it is the centre-backs who almost do the damage, with Clark keeping the ball alive and poking it to Duffy, who fires a low effort a couple of yards past the far post.

Painful one for Allen as he finds himself in a sandwich between Meyler and McClean. The midfielder looks dazed after what was a hefty collision, and Coleman will be hoping that he is able to continue here.

The physios have made the dreaded sign to the bench which means that Allen will have to come off here. It was a jarring collision and clearly there are concerns over a possible concussion for Allen. Wales are taking no risks despite the importance of this match.

what a huge blow that is for Wales. It didn't look quite bad enough for it to end Allen's game, but it looks as though the main damage was done in the landing as his head hit the ground very hard.

WALES SUB: There is the change as Allen departs to be replaced by Jonny Williams.

williams is immediately involved with a cross into the middle which Clark tries to deal with, only to slice his attempted clearance narrowly wide of his own goal.

CHANCE! The resulting corner goes all the way through to Davies, but the Tottenham man never looks set and sends an unconvincing right-footed effort off target.

UPDATE: We have some goals! Finally the deadlock has been broken in tonight's matches, with Macedonia grabbing a quickfire brace against Liechtenstein and Iceland now leading Kosovo. Nothing of great interest to Wales or Ireland, though.

Wales have enjoyed 71% of the possession in this last 10 minutes, but they are not doing enough with it. Ireland are offering very little going forward, but they have shown enough threat from set pieces already to suggest that, if they can stay in the game, then they could get a chance to nick it.

Serbia remain level with Georgia elsewhere in Group D, which means that as things stand a win would be enough to send Wales to the World Cup automatically. Still a long way to go, though, and plenty of scope for twists and turns yet.

There will be two minutes of added time at the end of this first half.

SAVE! Brady collects the ball on the right flank and cuts inside before trying to fizz a cross/shot into the near post which Hennessey collects comfortably.

The referee brings an end to the first half at the Cardiff City Stadium, and we're still goalless after a tight and tense opening 45 minutes between Wales and Ireland.

The hosts have controlled the possession so far, but clear chances have been few and far between at either end of the field. Ireland's best chances have come via set pieces, while Wales have largely been limited to long-range efforts.

Wales did clip the crossbar as early as the eighth minute when Aaron Ramsey's long-range effort was tipped onto the woodwork by the keeper, although it was always rising and even without Randolph's touch may not have ended up in the back of the net.

Aside from that, there has been only a Robson-Kanu header, long-range efforts from Allen and Lawrence and an opening for Davies to speak of for the hosts despite their dominance of possession.

Ireland have threatened through Hendrick and Duffy from set pieces, but neither were able to make the most of presentable chances following some questionable defending from Wales.

Chris Coleman's biggest concern from that opening 45 minutes will be the loss of Joe Allen, though. The influential midfielder was forced off in the 37th with a head injury after landing heavily following a collision with two Irish players.

In truth, it hasn't been the most exciting contest so far, but it has been full-blooded between these two sides.

We should hopefully have more goalmouth action in the coming 45 minutes, though, as Ireland need a win to stand any chance of qualifying, while a draw may not be enough for Wales either.

KICKOFF: Wales get us back underway for a huge second half in Cardiff! The biggest 45 minutes on Welsh soil for some time awaits the national side!

Wales are again looking to get on the front foot in the early stages of this half. Since Allen has gone off, though, they haven't looked as dangerous going forward.

A huge cheer ironically greets a challenge from Arter on Lawrence, which stopped the Wales midfielder in his tracks just as he was trying to break clear. Lawrence has been good in the middle of the park for Wales tonight.

CLOSE! This is the closest we have come so far! Chester gets in front of his man from a corner and flicks his header towards the near post, but it ripples the side-netting on its way behind.

Plenty of Welsh fans thought that one had gone in, but Ireland survive!

SAVE! Wales are knocking on the door now! Randolph is called into his first serious piece of action tonight, pulling off a fine reaction stop to deny a really good header from Robson-Kanu. Jonny Williams was the creator down the right, but Robson-Kanu's effort was matched by Randolph.

the resulting corner arrives all the way to Chester at the back post, but he plants his header comfortably over the crossbar.

This match is starting to come to life now! Those two Wales chances have cranked the volume levels back up inside the Cardiff City Stadium and the game itself is beginning to get a little more open too.

Oh my word, what a huge goal this could be! It comes from nothing, but McClean silences the Cardiff City Stadium with the opening goal!

It stems from Hennessey as he rolls the ball out to Williams, who immediately finds himself under pressure from Hendrick. The Burnley man blocks the clearance, and then takes advantage of some lax defending to burst down the right flank - just about keeping the ball in play.

His delivery from the right goes all the way through to McClean, who plants an unerring first-time finish home.

A huge half an hour or so awaits both of these two teams now, and it is really balanced on a knife edge at the moment. A draw, as things stand, would still be enough to reach the playoffs, but right now it is Ireland who are finishing second.

Wales were on top in this game before that goal. They had created two good chances in this second half and the crowd was in full voice before McClean opened the scoring to stop them in their tracks. The hosts need to rediscover that momentum quickly.

UPDATE: More bad news for Wales as Croatia have taken the lead against Ukraine in Kiev, which means that as things stand Chris Coleman's side would need a win to make it into the playoffs.

Incidentally that doesn't change anything for Ireland, who will reach the playoffs with victory regardless of what happens elsewhere.

Big block from Duffy as he throws himself in the way of a shot from Davies, who took one too many touches before going for goal. Wales want a handball, but the referee is having none of it.

WALES SUB: A second change for Wales sees young Ben Woodburn replace King.

It is not looking good for Wales at the moment, but there is still more than 20 minutes for it all to change.

As things stand their World Cup dream will end tonight and even a draw wouldn't be enough for them to qualify for the playoffs, but should they find two goals in these closing stages then they would actually win Group D and qualify automatically. These are such fine margins!

UPDATE: Things go from bad to worse for Wales, who would still make the playoffs with a draw here and a draw in Kiev. Croatia have just scored again agaibst Ukraine now, which means that it is all up to Wales. They need two goals without reply.

YELLOW CARD! Murphy goes into the book for Ireland for a swinging arm on Ramsey.

UPDATE: The bad news keeps on coming for Wales - Serbia have broken the deadlock against Georgia which means that even a Wales win now would only get them into second place.

WALES SUB: A final throw of the dice for Chris Coleman as Sam Vokes replaces Robson-Kanu.

Less than 15 minutes remaining for Wales to pull something special off now! The hosts have controlled possession since that opening goal and are camped in the Ireland half right now, but they haven't been able to create any chances since going behind.

IRELAND SUB: Ireland make another change as Glenn Whelan replaces Arter.

YELLOW CARD! Out comes the yellow card for time wasting against Clark, which at least brings one cheer from a bunch of pretty unhappy Welshmen and women at the moment.

Those Welsh fans attempt to stir their team into life in the final 10 minutes with another rendition of their national anthem. It is not quite as hearty as the rousing rendition before kickoff now, though.

It is worth noting that this remains a very tense period for Ireland too. Wales need two goals to reach the playoffs, but if Ireland concede and this game ends 1-1 then both would miss out if other results stay the same.

Wales are getting more and more frustrated here, as you might expect. Ireland have managed this game masterfully since taking the lead, but they are still just one goal away from elimination. This could not be much tighter.

CHANCE! Late chance for Wales as Williams peels off his man at the back post, but he doesn't connect with his header well enough and McClean is able to hack it clear.

One final roar of defiance from the Welsh fans as the fourth official indicates a minimum of FIVE minutes added time.

IRELAND SUB: Another Ireland change to waste a bit more time as Kevin Long replaces Murphy.

YELLOW CARD! McClean picks up a late yellow card for a kick at Ramsey when going for the ball.

SAVE! One final effort from Ramsey goes straight into the arms of Randolph.

YELLOW CARD! Silly from Meyler as he goes into a needless sliding challenge on Hennessey picking up a yellow card which will see him miss the first leg of the World Cup playoff.

It is agony for Wales, but ecstasy for Ireland as they book their place in the World Cup qualifying playoffs.

The visitors were tactically superior to their hosts this evening, keeping Wales at bay and hitting them during the one defensive lapse Coleman's side made. James McClean got the only goal of the game and leads the celebrations, with Ireland now just two matches away from reaching their first World Cup since 2002. For Wales, though, the wait goes on.

Right, that is all we have time for this evening!

Thank you very much for joining Sports Mole for tonight's match as Ireland beat Wales in Cardiff to reach the World Cup playoffs at their hosts' expense. I will leave you with our match report, and be sure to stick around for reaction from both camps too. The final round of European World Cup qualifiers take place tomorrow night, so be sure to check back in for that!

From me, though, it is goodbye for now!