Rafael Benitez confirmed that Martin Skrtel will have a scan on the knee he twisted during Liverpool's thrilling 3-2 win over Manchester City.
The 23-year-old Slovakia international sustained the injury in the closing stages of the exciting Eastlands clash.
"Martin has twisted his knee and we will have to wait for the scan but we think it could be serious," said Benitez.
"That's the bad news for us today. When a player like Martin is on the ground you know it's serious so we will keep our fingers crossed that it won't be too bad."
Meanwhile, Benitez praised his side's second-half display after they came back from two goals down to claim all three points against Mark Hughes' team with a 3-2 victory.
He added: "The positive thing was the reaction of the players after a bad first half. We made two mistakes for both goals and the reaction and character we showed in the second half was for me the key to winning the game.
"I told the players at half-time to try and score one goal and then we would be right back in the game. That was the idea and the character and determination of the players was much better than the first half.
"We were pushing hard in the second half and the determination of the players was fantastic.
"The problem in the first half was we were making mistakes against players with ability and pace.
"It's better for me that we don't concede goals but at least if you can win it shows the players are ready for winning every game. Physically we are in good condition so credit to our fitness coach. We also have great belief and mentality."