Liverpool dropped points at Anfield for the first time this season after conceding an 82nd-minute equalizer to draw 1-1 against lowly West Bromwich Albion on Sunday.
The champions looked set to move five points clear for the biggest lead of their Premier League title defence so far thanks to Sadio Manes 12th-minute goal.
However, what had been a one-sided match changed when Liverpool centre back Joel Matip was forced off injured in the 60th minute.
And from one of West Broms half-chances, Semi Ajayi rose above Fabinho to head the ball in off the far post, allowing West Brom to snatch a point despite only enjoying 22% possession.
It was Sam Allardyce's first away match in charge of West Brom after taking over a team likely to be embroiled in a relegation scrap this season. He is known as a survival specialist and this is the type of battling result Big Sam is known to secure, against the odds.
Liverpool has a three-point lead over second-place Everton, its close neighbour on Merseyside. The Reds had won their first seven home matches.