Jurgen Klopp again pointed the finger at the fixture schedule after Liverpool were left sweating on the fitness of James Milner.
Milner pulled up after only six minutes of the FA Cup third round tie against the Blues at Anfield on Sunday, which the Reds went on to win 1-0.
The 34-year-old underwent treatment on his left leg for several minutes before limping off the field with what appeared a hamstring or thigh problem. He will have scans to determine the extent of the damage on Monday.
Klopp, a long-time critic of the demands placed on players, made nine changes from the side that beat Sheffield United in the Premier League on Thursday with Milner and Joe Gomez the only two to keep their places.
And he said: “Milner has pain and that is serious. It's muscle.
“Two players started from the last game and one got injured.
“That's the situation we are in and that's why a lot of managers make changes. It’s not to do with the cup, it’s just the timing of the game.”
Klopp at least had the encouragement of Alex Oxlade-Chamberlain returning to action as a second-half substitute after missing Liverpool's festive period with an ankle problem.
“It was a nice add-on to have Oxlade-Chamberlain back,” said the Reds boss.
“He looked pretty lively when he came on. He trained only for two days, that's why he didn't start.”
