Hello and welcome to Sports Mole's live text coverage of the World Cup clash between Portugal and Spain at the 45,000-capacity Fisht Olympic Stadium. This is arguably the pick of the group-stage fixtures, as the 2010 tournament winners take on the reigning European champions in what should - fingers crossed - be a thrilling contest.

GROUP B RESULT! The full-time whistle has just sounded in the early kickoff between Morocco and Iran, which finished 1-0 to the latter. A goal in the very final seconds earned Team Melli just their second-ever victory at a World Cup finals, placing them top of the standings. That could very well spell the end of Morocco's tournament after just one match!

SPAIN TEAM NEWS!

STARTING XI: De Gea; Nacho, Pique, Ramos, Alba; Busquets, Koke; Silva, Isco, Iniesta; Diego Costa

SUBS: Carvajal, Saul, Rodrigo, Thiago, Lucas, Odriozola, Arrizabalaga, Azpilicueta, Monreal, Iago Aspas, Asensio, Reina

Starting with a look at the Spain team, stand-in boss Fernando Hierro has decided to go with Diego Costa as the focal point up top. La Roja have plenty of options in attack, leaving some to wonder whether he would go with a strikerless system this evening. That will not be the case, though, as the Atletico Madrid ace is given the nod up top, with support provided by a three-man attacking midfield.

David Silva, Andres Iniesta and Isco were always likely to get the nod either side of Costa, and Hierro - or was it perhaps predecessor Julen Lopetegui who selected this starting lineup? - has gone with Koke alongside Sergio Busquets in the holding position. Thiago Alcantara was another option, but he has been overlooked, while Iago Aspas is one of many attacking options from the bench.

The only surprise, if you can call it that, is the inclusion of Nacho at right-back. Dani Carvajal is still nursing an injury picked up in Real Madrid's Champions League final win against Liverpool a few weeks back, but Alvaro Odriozola appeared the favourite to fill in. On the opposite flank is Jordi Alba, coming off the back of another solid campaign for Barcelona, while Gerard Pique, Sergio Ramos and David de Gea complete the back five.

PORTUGAL TEAM NEWS!

STARTING XI: Rui Patricio; Cedric, Pepe, Fonte, Guerreiro; Carvalho, Moutinho; Fernandes, B.Silva, Guedes; Ronaldo

SUBS: Alves, M Fernandes, A.Silva, Joao Mario, Lopes, Ruben Dias, Ricardo, Gelson, Mario Rui, Quaresma, Beto, Adrien

In terms of the European champions, Fernando Santos has made a big call by using Goncalo Guedes from the off. The Paris Saint-Germain youngster is coming off the back of an impressive season on loan at Valencia and, combined with his two-goal showing in the friendly win against Algeria last week, he has done enough to be selected in the starting XI. No surprise to see who will lead the line - Cristiano Ronaldo remains the undisputed star of this side.

Bruno Fernandes is another who impressed last time out, so Santos will use the Sporting Lisbon midfielder alongside Guedes and Bruno Silva in a three-man attacking midfield, meaning that Andre Silva has to settle for a place on the bench. The other big selection call comes at centre-back, where Jose Fonte returns to the starting lineup alongside the vastly experienced Pepe.

Cedric Soares is selected over Ricardo Pereira at right-back, and on the opposite flank is Raphael Guerreiro of Borussia Dortmund. Goalkeeper Rui Patricio is now a veteran of sorts on the international stage, meanwhile, even if he is still aged just 30. No surprises in the defensive midfield zone, either, as Santos has gone with William Carvalho and Joao Moutinho, who provide different qualities to this side.

Fernando Santos has decided to leave Andre Silva out of his starting lineup and instead go with a three-man midfield comprised of Bernardo Silva, Goncalo Guedes and Bruno Fernandes. This system, spearheaded by Ronaldo, worked a treat in the 3-0 win against Algeria last week. Ronaldo is the undisputed star of the side, boasting 81 goals in 150 senior internationals. Spain's big selection call is the inclusion of Nacho at right-back over the half-fit Dani Carvajal and youngster Alvaro Odriozola.

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Spain head into this game in a state of disarray according to many, having parted company with manager Julen Lopetegui just two days before this mouth-watering opening fixture. Fernando Hierro is now tasked with taking this side forward, for the next month at least, but his only previous managerial experience came with Real Oviedo where he spent one season. In at the deep end? Well, this is not the worst group of players to take charge of...

While most teams would probably crumble if they lost their manager on the eve of a major tournament, particularly one who was clearly very popular with his players, this Spanish side just do not look like they are about to fall apart. La Roja bombed at their past two tournaments, granted, but they have looked something close to their best over the past two-year cycle.

Spain must still be considered in the top band of favourites to go all the way, along with France, Brazil and Germany, even if their sporting director has had to step in and manage the side. It is not ideal, but La Roja boast talent aplenty and should - should! - be just fine. Their dominance between 2008 and 2012 is now a thing of the past, having looked poor at the last World Cup and at Euro 2016, yet under Lopetegui they found their groove again.

Under Lopetegui, Spain dropped just two points in qualifying - a 1-1 draw with Italy early on - and ended with a record of 36 goals scored and just three conceded. No team in UEFA qualifying had a better defensive record than the 2010 World Cup winners and in De Gea, Alba, Pique, Ramos and the unfit Carvajal they surely have the best backline in the competition. It must be said that their midfield and attack line is not all that shabby, either!

There is a nice blend of youth and experience in the squad, and their options have only been added to up top since Costa pledged his allegiance to Spain in 2014. La Roja have actually gone 25 years since last losing a World Cup qualifier following their latest unbeaten campaign, which does of course mean that they were much-fancied heading into the previous edition in Brazil.

Spain lost to Chile and the Netherlands at the 2014 World Cup, becoming the latest reigning champions to fall at the first hurdle. Even if their preparations have been disrupted this week, there is little risk of La Roja failing to reach the last 16, but top spot is what they are after. If they are to edge out the Selecao for that favourable first knockout-round tie, defeat must be avoided today.

Prior to losing their manager, Spain thrashed Costa Rica and Argentina - Isco scoring a hat-trick in the latter of those friendlies - while also playing out a 3-3 draw with Russia, a 1-1 draw with Germany and a 1-1 draw with Switzerland. Not exactly the best of warm-up results, and even the 1-0 victory against Tunisia was a little disappointing as La Roja failed to move through the gears.

Results may not have been great, but Spain have now gone 20 matches since their last defeat - a 2-0 reverse at the hands of Italy at Euro 2016. During their unbeaten qualifying campaign to reach Russia, La Roja scored first in every game and went on to win all but one of those - again coming unstuck to Italy, who claimed a 1-1 draw. Put simply, the one-time World Cup winners do not lose many games, and when they edge in front you have very little chance of recovering.

All was looking rosy for Spain just a few days ago; then came an announcement from Real Madrid that Julen Lopetegui would become their next manager. La Roja chiefs acted swiftly by axing Lopetegui, who has been in charge for the entire qualifying process, and installing sporting director Fernando Hierro in his place. Having looked so impressive on the road to Russia, albeit with some underwhelming friendly results, Spain now need to regroup under a new man.

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Portugal, it is safe to say, are a lot more settled than their opponents. The Selecao head into this tournament sitting fourth in the latest FIFA rankings, behind only Belgium, Brazil and Germany, and they are considered among a batch of seven or eight teams with a realistic chance of lifting the trophy next month. If you listen to the bookies, Fernando Santos's men are the eighth favourites.

Even England have a better chance of succeeding, according to those odds, but Santos would not want it any other way. Portugal were similarly ranked heading into Euro 2016, and we all know what happened next. The Selecao managed to do just about enough to reign on the continent, famously picking up just one victory in normal time all tournament - that coming against Wales in a one-sided semi-final.

The way Portugal beat the odds to go all the way in France has given plenty of sides hopes of something similar happening in this competition, although it does come with the caveat that they just happen to have arguably the greatest footballer of all time in their ranks. Cristiano Ronaldo scored a further 15 goals in qualifying, taking him to 81 in all for his national side, and he also bagged 43 for Real Madrid in 2017-18.

Portugal started their World Cup qualifying campaign with a 2-0 defeat to Switzerland, before hitting back with wins in each of their next nine matches - including victory by the same scoreline against the Swiss on the final matchday to seal their place in Russia. The European champs ended their campaign with 32 goals scored and just four conceded - one more than today's opponents - but the calibre of the opposition does have to be taken into account.

The Selecao have played seven friendlies since qualifying for the World Cup last autumn, beating Saudi Arabia, Egypt and Algeria, but drawing with United States, Tunisia and Belgium, while also going down 3-0 to tournament absentees Netherlands. Warm-up matches cannot be viewed too seriously, however, and in competitive matches Portugal have lost only one of 29 under Santos.

That record reads two defeats in 29 when accounting for last summer's penalty shootout loss to Chile at the Confederations Cup. Portugal have relied largely on some familiar faces over this two-year cycle, as the so-called golden boys of Euro 2016 - the poster boy being Renato Sanches - have simply not pushed on. That is not to say that there are no talented youngsters around, though, with Guedes a favourite of many to win the Young Player award in Russia.

DID YOU KNOW? Portugal have not won their opening fixture at a World Cup or European Championship since 2008, and they have also lost their opening match in qualifying for the past two major competitions. The Selecao are perennial slow starters, as witnessed at Euro 2016 when somehow scraping their way through a rather poor group on paper.

PREVIOUS MEETINGS! These two sides have met on 36 previous occasions, with Spain winning exactly half of those and losing just six. This is a fixture that La Roja may have dominated overall, but results have been mixed over the last 16 encounters since 1950 - five wins for Portugal and seven draws in that time. The most recent contest came at Euro 2012, when Cesc Fabregas scored the winning spot kick after a goalless draw.

With kickoff at the Fisht Olympic Stadium now less than five minutes away, let us check out some pre-match thoughts from both camps.

Fernando Santos: "Spain has played the same way for 10 years before. I don't expect any surprises. It does not seem to me that there is a disadvantage on the part of Spain. I do not expect any surprises. There will be two on-field teams that will want to win the game. The most important thing is the clash between the two teams. It has everything to be a great game. We are prepared for a tricky game but we are confident that we are capable."

Fernando Hierro: "We've come to fight for the World Cup. We have a great opportunity and that should be the focus. I know they're going to give 100%. In a World Cup nobody gives anything away. We all know what this means and our responsibilities. When the president told me the possibility, I had three choices: to say no, another was to go and the third was to stay - to take a step forward for the Spanish federation and for Spanish football. I couldn't say no because I would not forgive myself."

Santos clearly does not believe that his side have any sort of advantage today, as Spain know exactly what the gameplan is and will stick to it no matter who the manager. It is a fair assessment - had this happened to 90% of other sides in this competition, you would tip them to completely bomb. As it is, La Roja have far too much talent throughout their squad and should be fine. Still, what was always going to be a big game has now become even bigger. Bring it on!

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KICKOFF! Spain, sporting their changed away strip in Sochi this evening, get us under way in the pick of the group-stage fixtures. Portugal, the reigning European champions, are looking to make a fast start at the Fisht Olympic Stadium.

PENALTY TO PORTUGAL! Explosive start to this match! Cristiano Ronaldo was sent to the ground by Nacho following a couple of step-overs. A penalty is awarded, but to me it looked like the Real Madrid ace made the contact with his clubmate rather than the other way around.

In his 36th outing at a major tournament, Cristiano Ronaldo gives Portugal the lead from the penalty spot. The Real Madrid superstar stuck the ball to David de Gea's left; the keeper went the opposite way. After seeing a replay, the referee did appear to make the right call with that decision.

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Any chance of Spain being given a chance to settle into the match has certainly gone with that Ronaldo penalty. Again, though, there is plenty of experience throughout this Spanish side and it will take more than that to knock them off their feet.

Spain with plenty of the ball since falling behind, as you would expect, but so far they have been unable to really get it into the final third. Portugal with just the one attack so far, culminating in the move that led to Ronaldo's penalty.

SHOT! Spain's first half-chance to level up the contest falls the way of David Silva who, despite being in good goalscoring form for his national side this season, cannot keep the awkward volleyed attempt on target.

With that early goal, Ronaldo becomes only the fourth player to score in four World Cups, after Uwe Seeler, Pele and Miroslav Klose. Does he have another tournament in him? Possibly, but his powers will surely wane before then.

La Roja starting to dominate the game now and, unlike in the previous 10 minutes or so, they have popped up in dangerous zones over the last five minutes. That could suit Portugal - they have the perfect man in Ronaldo to lead their counter.

I've already change my mind once with that Ronaldo penalty call and I'm tempted to revert back to my original decision. Nacho did make contact with his Real Madrid teammate, but Ronaldo knew exactly what he was doing and made the contact first.

Guedes, a real star in the making, has half the length of the field to run as Portugal are given another chance to counter. The youngster never looked comfortable up against Ramos, though, and was forced into a blocked shot from 30 yards.

YELLOW CARD! Sergio Busquets is the first player of the evening to be shown a yellow card after following through on Goncalo Guedes. Cristiano Ronaldo, with one goal to his name already, blasts the free kick into the wall.

CHANCE! Brilliant play from Iniesta in his final international tournament. The ball was cut back for David Silva, whose shot was deflected wide. Nothing came from the corner and, after mounting a counter-attack, Guedes should have done a lot better when picked out in the middle - a poor first touch denied him the chance of a proper shot, with Alba getting a block in.

A superb individual goal from Diego Costa! The Atletico Madrid used his strength to hold off his man and, after delaying the shot for what felt like an age, he picked out the bottom corner of Rui Patricio's net. VAR is required as Costa was a little rough when winning the ball off Pepe in the build-up, but the goal has been awarded.

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OFF THE BAR! This match is living up to the hype - and then some! Isco with an absolute belter of a shot from distance, which hit the underside of the crossbar. The referee's watch informed him that it did not cross the line, despite Isco's protests.

YELLOW CARD! On the incident in the build-up to Spain's equaliser, Costa did make contact with Pepe but the referee was justified in allowing play to continue. Bruno Fernandes has just joined Sergio Busquets in the referee's book for a strong challenge.

Well today's first two games were a little boring, to say the least, so thank goodness for this thriller being staged by Portugal and Spain. Just the two goals so far, but talking points aplenty and we will surely see that tally added to.

A little over half an hour played in Sochi and Spain are the side in control of possession. That has been the case pretty much throughout, although Portugal look very dangerous when given the chance to counter-attack.

A controversial penalty call, a trademark goal from Diego Costa, a bullet of a strike against the crossbar and a couple of decent chances missed - it has been the best first half of the World Cup so far, and we still half 10 minutes to go before the interval.

CLOSE! Spain have played some brilliant football today. Another impressive move culminates in Jordi Alba pulling the ball back for Andres Iniesta, whose shot ended inches wide of the far post after taking a touch on its way through.

There has been no change to the flow of the match - Spain are dominating possession, and looking lively every time they get into the final third, while Portugal are dangerous on the counter. Six minutes to go of a gripping first half.

One of Portugal's better spells on the ball over the past couple of minutes, keeping hold of possession but not really doing a great deal with it. La Roja look some incredibly composed as soon as they win it back, going from back to front with ease.

SAVE! Not the cleanest of strikes from Spain's star performer in Isco, who made some space on the edge of the area and got a shot away at the end of the move. Rui Patricio got behind it without having to break stride.

The best goalkeeper in the world has just had an absolute howler! Cristiano Ronaldo, with barely any backlift, gets a shot away from 20 yards which went right through the hands of David de Gea. Portugal will take a one-goal lead into half time.

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Portugal take a 2-1 lead into half time thanks to a brace from Cristiano Ronaldo. It has been a thrilling opening 45 minutes at the Fisht Olympic Stadium, with Spain striker Diego Costa netting either side of Ronaldo's two goals.

The big selection call made by the stand-in boss was to field Nacho at right-back in place of the half-fit Dani Carvajal, despite Alvaro Odriozola filling in for the warm-up matches. That would prove a big call as, after just two minutes of an action-packed first half, Nacho stuck out a leg and Cristiano Ronaldo took full advantage of the contact inside the box.

In response, David Silva sent a couple of chances wide as Spain took control of possession, patiently probing away for an opening. Portugal were happy to live off counter-attacks, though, and they should have doubled their tally through one such move as only a poor first touch prevented Goncalo Guedes from converting inside the box. Moments later, Diego Costa showed his qualities of old as he aggressively won the ball from Pepe, held off Jose Fonte and then picked out the bottom corner.

Buoyed by that impressive individual strike, Isco sent a bullet strike against the underside of the bar - goal-line technology confirming that it did not cross the line, despite the midfielder's protests. Andres Iniesta then came close following some good play from Jordi Alba down the left, and Isco's effort from the edge of the area was right at Rui Patricio. Portugal went into the interval a goal in front, though, with Ronaldo's 20-yarder somehow squirming through the hands of David de Gea.

BENCH WATCH!

PORTUGAL SUBS: Alves, M Fernandes, A.Silva, Joao Mario, Lopes, Ruben Dias, Ricardo, Gelson, Mario Rui, Quaresma, Beto, Adrien

SPAIN SUBS: Carvajal, Saul, Rodrigo, Thiago, Lucas, Odriozola, Arrizabalaga, Azpilicueta, Monreal, Iago Aspas, Asensio, Reina

Spain arguably had the better of the first half - which the stats here back up - but it is Portugal who have that one-goal lead to protect in Sochi.

RESTART! Portugal get us back under way at the Fisht Olympic Stadium in Sochi, sitting comfortably thanks to star man Cristiano Ronaldo's first-half double. Neither manager has made a change at the interval, so it is as you were.

Ronaldo now has 22 goals in his last 18 outings for Portugal, and remains on course for a World Cup hat-trick. The Real Madrid ace and teammate Bernardo Silva have both slipped on the surface, which looks pretty wet after being heavily watered.

The second half has not taken off in the same manner as the first just yet. Both sides looking a little disjointed, which will obvious suit Portugal a lot more than their opponents, who are chasing a goal or two in the remaining minutes.

As you can see from the stats here, Spain are in complete control when it comes to possession of the ball. La Roja have looked lively in the final thrid, too, finding the target three times.

Plenty of 'almost' moments for the 2010 World Cup winners in the opening 10 minutes of this second half. It is not quite happening for Hierro's charges at the moment, though, and opposite number Santos will be pleased with how things are panning out.

Well that is the equivalent of the commentator's curse! I'd just mentioned how Spain had failed to really get going since the restart, and right on cue Diego Costa bags his second of the evening. A deep free kick was headed back across goal by Sergio Busquets, with the striker there to tap home from close range.

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For all of Spain's impressive build-up play today, their first goal came via a Busquets punt forward and the second via a headed knockdown. A little over half an hour to play here and it is very much all to play for - good luck calling this one!

Spain edge in front for the first time tonight through an unbelievable Nacho strike! Guilty for giving away the penalty for the first goal, the full-back put his boot through the ball from 20 yards out and sent it flying past Rui Patricio.

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That Nacho goal really was special. The ball bounced just in front of him yet he made perfect contact, sending it in the only place that Rui Patricio could not reach. How will Portugal react to Spain's quickfire double?

Bernardo Silva with a couple of stupid challenges but he avoids being booked by the referee. Portugal boss Fernando Santos is now readying Joao Mario to come on, with that change likely to be made in the next couple of minutes.

Portugal have been made to wait a couple of minutes to make that change as the ball has yet to go out of play! Spain had been playing the better football but that has changed over the past couple of minutes; the Selecao now on top.

PORTUGAL SUB! Joao Mario has finally been introduced in place of Bruno Fernandes. A few different options on the bench for Santos to turn to, including Andre Silva, but his first roll of the dice comes in the middle of the park.

SUBS! Spain make their first change of the evening, bringing on Thiago Alcantara for the tiring Andres Iniesta in central midfield. Portugal have made their second alteration, meanwhile - Ricardo Quaresma is on for Bernardo Silva.

CHANCE! Diego Costa misses a big chance to score a World Cup hat-trick. The ball was cut back to the striker in the middle of the box, but he dragged the subsequent shot wide of Rui Patricio's goal.

Portugal starting to make chances of their own, but there has been nothing clear-cut for a while. At the risk of cursing Spain, Cristiano Ronaldo has been a little quiet of late... There does look to be a sixth goal in this match.

This game really has flown by - less than 15 minutes left to play in Sochi! It has undoubtedly been the game of the tournament so far, more than living up to its pre-match hype. Five goals so far and still plenty of time for another.

SPAIN SUB! Ricardo Quaresma gets a shot away but it lacked quality and was never going to test David de Gea. Iago Aspas has just been brought on for the final 12 minutes, taking over from two-goal striker Diego Costa.

Both managers have one more substitute available to make, and I'd be surprised if Andre Silva is not one of those brought on for Portugal. Stand-in Spain boss Hierro is more likely to shuffle his pack in midfield than up top, on the other hand.

PORTUGAL SUB! Cedric Soares with a decent delivery over the top for Cristiano Ronaldo, who could not get to the ball before Gerard Pique. The centre-back was clattered by a couple of other players and is now receiving treatment. During the stoppage, Andre Silva has been brought on for Guedes.

SAVE! Iago Aspas gets a shot on goal that is hit far too central, allowing Rui Patricio to gather. That came at the end of another impressive passing move from Spain, who are doing well to close this game out.

SPAIN SUB! Lucas Hernandez has been brought on for David Silva to help close out the final stages of this gripping match. Danger for Spain, though, as a free kick has just been conceded 25 yards from goal...

Put this match down in World Cup folklore! Cristiano Ronaldo sends the free kick up and over the wall to complete his hat-trick - the 51st in World Cup finals history, and also the 51st of his professional career. What a game!

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The 90 minutes are up in Sochi, but everyone in the ground and watching around the world would happily take another couple of hours of this. Ronaldo's dipping free kick is the icing on the cake of what has been an unbelievable match.

Four minutes have been added on at the Fisht Olympic Stadium, and we have now played half of those. Quaresma takes the ball past a couple of players but his shot is blocked when the goal opened up for him. Ronaldo then glanced a header wide.

How on earth do you go about analysing a game like that?! Cristiano Ronaldo's 51st career hat-trick is the headline news from Sochi - it was also coincidentally the 51st treble scored in World Cup finals history - but there is so much more than just that to take away from this match. Diego Costa also netted twice and Nacho scored a screamer, while David de Gea's howler for Ronaldo's second goal has almost been forgotten.

That concludes Sports Mole's live text coverage of events from the Fisht Olympic Stadium. An on-the-whistle report can be found by clicking here, and be sure to join us again tomorrow for updates from four - yes four! - more World Cup games. See you then!