Chelsea boss Jose Mourinho confirmed Ashley Cole had suffered a serious knee injury after being carried off in Wednesday's 3-0 Premiership win over Blackburn.
The England defender caught his studs in the Stamford Bridge turf while attempting to control the ball and immediately fell to the ground clutching his left knee.
The left-back is almost certainly out of the England squad for next week's friendly against Spain at Old Trafford and could miss the rest of the season if he is diagnosed with cruciate ligament damage.
Goals from Didier Drogba, Frank Lampard and substitute Salomon Kalou gave Chelsea and easy win but Mourinho declared: 'I don't exactly know what Ashley has done but it is serious - it must be because he cannot walk.
'The injury is in the knee and we have to wait for a couple of days to find out exactly what it is.
'I am not sure how he did it but he has a problem with his knee ligaments.'
Mourinho is thankful that Cole's international understudy Wayne Bridge is fit to replace him and also revealed defender Khalid Boulahrouz is set to return to training after recovering from knee ligament problems.
But Mourinho would not be drawn on the possible return of captain John Terry against Charlton this weekend or his inclusion in Steve McClaren's England squad.
Mourinho added: 'In this moment we have Wayne Bridge who is playing a lot and playing well.
'But it means I have less options. Because we have no wingers, Bridge is a player I could have used as an outside left. So in this moment I have only one left-back.
'We are doing so many things to have a team to compete in all competitions and we must compete without Ashley.
'Khalid Boulahrouz will train with the group for the first time on Thursday and maybe in one more week he can play.
'I have to make a decision about whether to play John Terry this weekend against Charlton or the game afterwards against Middlesbrough.
'He is quite close to coming back but I have not spoken to Steve McClaren about him. First, we have to see if he plays against Charlton or not and what the reaction is after the game.'
Mourinho though was full of praise for his front pairing of Andriy Shevchenko and Didier Drogba, who ran Rovers ragged all night.
Mourinho added: 'For me Shevchenko was brilliant, brilliant - it was his best game so far for us.
'He doesn't need to score goals to play brilliant. He did things he has never done before so it shows that step after step after step, he's going in the right direction.
'He was fighting, he was strong in the duel and always in the right place.
'He was aggressive and always in dangerous positions - for me he was brilliant.
'Didier has been `up' from the first game of the season - never `up and down'. He was chasing people and helping in defence. This is the kind of player who gives you that something extra which wins matches and trophies.'
Mourinho also mentioned the performance of German midfielder Michael Ballack, who was barracked by home fans throughout the game.
He added: 'He made a big contribution for me - maybe not for the fans - but for me he made a big contribution.
'Because I pick the team - not the fans - if he makes me happy and gives me what I want, he's okay.
'It's obvious this football in England is faster than anywhere else in the world and it is not easy to adapt. But he gives everything for the team.'
Blackburn manager Mark Hughes was disappointed with the result but happy with the positive performance his side produced.
Hughes said: 'We came here to try to win the game. We didn't try to frustrate Chelsea.
'We made a bright opening but we allowed Drogba in for the first goal. But overall we kept possession in midfield and caused them some problems.
'But then Frank Lampard, who I thought had a quiet game, produces a fantastic strike and that's the quality Chelsea have when they are not playing well.
'They have players who can produce individual pieces of magic and win matches. I am disappointed with the result but happy with the performance.
'We asked questions of Chelsea and not many teams do that or create as many chances as we did. We just didn't take our opportunities when we had them.'