Liverpool midfielder Mohamed Sissoko is expected to be sidelined for the next three months.
The Mali international suffered a shoulder injury playing against Birmingham in the Carling Cup.
A statement on the Liverpool website read: 'Unfortunately Momo will require surgery which is scheduled to take place next week.
'It is anticipated he will be out of action for three months.'
The former Valencia midfielder appeared to get in a fairly innocuous-looking tangle with Blues player Mehdi Nafti, and after treatment on the pitch he had to be carried off.
The player, 21, was assessed by club medical staff today after being kept in hospital last night and they decided he required surgery.
Sissoko has had bad luck with injuries in his short time at Anfield, suffering an eye injury in the Champions League last-16 clash with Benfica in February.
It was feared the injury could have left his vision permanently impaired but he made a full and quick recovery and coincidentally returned to action in the 7-0 FA Cup victory over Birmingham in March.
Fellow midfielder Xabi Alonso recognised that Sissoko's injury would force changes on manager Rafael Benitez, and would be happy to form a central partnership with Reds captain Steven Gerrard.
'If he's out, it's clear we'll have to change something in the team. There are times when we've played without him before and we've still managed to get good results,' Alonso told the club's official website.
'But now we will have to think of a new system and I'm sure Rafa will do something.
'Stevie and I have played together in the middle a lot. Sometimes it has worked really well and other times we've had some problems.
'We know we need to work together to find the balance which is important for the team.
'Stevie has massive qualities. He has an ability to get into the box and we have to make sure he's still able to do that because that's where he works so well.
'If the team is compact and we work as hard and show the same form we did last season, I'm sure the identity of the players in the position isn't important. It will be harder without Momo, but we can make it work.'