Liverpool's new defender Aly Cissokho is set to be sidelined for up to six weeks after suffering an ankle injury in his first start for the club.
Cissokho only joined the Reds on a season-long loan from Valencia earlier this month and the French left-back is already facing a spell out of action after sustaining the problem early in Tuesday's League Cup second round victory over Notts County at Anfield.
Liverpool boss Brendan Rodgers conceded former Porto and Lyon star Cissokho's injury was a significant blow ahead of Sunday's clash with arch rivals Manchester United.
"Aly Cissokho could be four to six weeks, which is a blow because he came in and trained really well last week," Rodgers said on Friday.
"But he is on crutches at the moment and we'll look at that over the coming weeks. But he certainly won't be available (on Sunday)."
Two other Liverpool players picked up injuries against County, with Ivorian defender Kolo Toure carried off on a stretcher due to a groin problem and Welsh midfielder Joe Allen limping off with a hamstring strain.
But Rodgers had more positive news on that pair, saying: "Toure's injury is nowhere near as bad as we thought.
"We will assess that over the next 24 to 48 hours. I think we were all thinking he might be out for longer after the game but he's made an excellent recovery.
"The diagnosis isn't anywhere near as bad as we thought, so we'll see how he is for this weekend.
"If it's not this weekend, then we would think after the international break he won't be too far away.
"Joe likewise - it was only a grade one strain, so he may be doubtful for the weekend but certainly after the international break, he'll be fine."