Liverpool defender Virgil van Dijk was forced off in the first half of the Merseyside derby following a challenge by Everton goalkeeper Jordan Pickford.
The Reds were leading 1-0 thanks to a goal from Sadio Mane after two minutes and 15 seconds at Goodison Park, the fastest scored in this fixture in the Premier League era.
Barely three minutes later, Fabinho looped the ball into the Everton penalty area towards Van Dijk and Pickford lunged into the centre-back, missing the ball.
Pickford was spared the risk of a penalty and possible card from the referee as Van Dijk was narrowly offside when Fabinho crossed.
Van Dijk was treated on the pitch but was unable to continue, walking gingerly down the touchline as Joe Gomez came on to replace him.
Any injury to the Netherlands international will be a huge blow to manager Jurgen Klopp, with Liverpool entering a packed run of matches until the next international break in November.
They play six times in the next three weeks, including Champions League games against Ajax, Midtjylland and Atalanta and a Premier League trip to Manchester City on November 7.