Liverpool's defeat at Southampton meant Jurgen Klopp's side have gone three Premier League matches without a victory for the first time since February 2017.
The loss came on the back of draws against struggling West Brom and Newcastle and the four-point lead the champions held at Christmas has evaporated.
By the time they play their next league match, at home to Manchester United a week on Sunday, their arch rivals are likely to have overtaken them.
Here, the PA news agency takes a look at why things have suddenly become more difficult for Klopp's side.
What is the problem?
Liverpool have won just two of their nine away league matches, dropping 16 points in total with five draws and two defeats. Draws on the road against Brighton, Fulham, Newcastle – all teams currently in the bottom six – have been particularly damaging. By comparison, on their way to winning the title last season they dropped just 13 points on the road. Teams at home have found a better way to combat Klopp's side and they are having more success at frustrating their opponents.
What has caused it?
Despite being the league's leading scorers the goals have dried up over the festive period. Apart from the 7-0 win over Crystal Palace, which is increasingly looking like an aberration, in the last five league matches Liverpool have scored more than one goal in a game only once when they beat Tottenham 2-1 in the 90th minute. Southampton was the first time since May 2018 Klopp's side failed to score in back-to-back league matches, which is an indicator of their previous consistency.
Who is at fault?
Roberto Firmino has scored just five goals in 17 league appearances, three of which came in back-to-back matches just before Christmas, Sadio Mane has two in his last 12 – also in successive games last month – despite offering a greater threat going forward. Mohamed Salah (13 in 16) is the only player showing consistency and he has drawn a blank in his last three matches. Diogo Jota, who with five goals is the only other player who has managed more than one league goal this season, is not due to return from injury until the end of January.
Why have the goals stopped flowing?
There has been a creativity vacuum in midfield as injury has robbed Klopp of Thiago Alcantara, Alex Oxlade-Chamberlain, Naby Keita and Xherdan Shaqiri for various parts of the season. The manager has had to rely heavily on captain Jordan Henderson, Georginio Wijnaldum and 19-year-old Curtis Jones in midfield – a trio which have contributed just two goals between them – with Jones the most attack-minded of the three.
So the midfield is at fault?
Not entirely. Much of Liverpool's success last season came from their marauding full-backs and while Andy Robertson has been the most consistent player this season, Trent Alexander-Arnold is struggling. The England right-back set an unwanted, new Premier League record for the season after giving the ball away 38 times against Southampton. Unfortunately Klopp's options at full-back are limited with Kostas Tsimikas out injured and teenager Neco Williams inconsistent.
Are there any underlying issues which could also be contributing?
Problems at centre-back – with Virgil Van Dijk and Joe Gomez likely to be out for most, if not all, of the season and Joel Matip regularly sustaining knocks – means it has been something of a muddle. Fabinho has played the majority of games in central defence, thus depriving Klopp of a key midfielder, and teenager Rhys Williams and the relatively-inexperienced Nat Phillips have been in and out of the team. The Henderson-Fabinho combination at Southampton was their 10th different starting centre-back pairing in 17 league matches, which has only added to the uncertainty.
