Emre Can is in doubt for Liverpool's match against Middlesbrough, according to manager Jurgen Klopp.
Can was not in the squad for the Reds' 2-2 draw at home to West Ham on Sunday after picking up a problem in training, while Dejan Lovren came off at half-time due to cramp.
Both players took part in training on Monday, but versatile Germany international Can may not be ready for the midweek Premier League trip to Teesside, with a fixture against neighbours Everton to follow next week.
"Emre was a challenge with Divock [Origi] in training, knee on knee," Klopp told a media conference on Monday.
"Both trained on and both could do the rest of the training, but Emre had a little bit more pain so we looked a little bit more exact on it and how I said yesterday, I never heard about this ligament, but it's a little bit damaged.
"He's already on a good way and I'm not sure - he's in doubt for Wednesday, but I think Everton he will be back for sure. It would be cool if he could train [on Tuesday], we will see. It's painful, not really more."
Liverpool had to come from behind to earn a draw against West Ham, a result that left them six points back from league leaders Chelsea.