Chelsea are facing a midfield crisis ahead of their Champions League semi-final against Liverpool next week.

Manager Avram Grant could be without Michael Ballack, Michael Essien and Frank Lampard for the first leg at Anfield on Tuesday.

Ballack suffered a hamstring injury in training on Wednesday which caused him to sit out the 1-0 victory at Everton last night, while Essien is suspended and Lampard is by his sick mother's bedside.

The trio are all considered first choices by Grant, although Essien would have probably played at right-back if he hadn't shown dissent and picked up his second booking of the knockout stages against Fenerbahce. Striker Didier Drogba is also battling to be fit for the Liverpool tie after missing Chelsea's last two matches with a knee injury.

Defender Ricardo Carvalho admitted Essien will be a big miss at Anfield, but is still hopeful Ballack will recover in time.

He said: "Michael is very important for us and we will miss him. He is strong, likes to get forward and always likes to help his team. He never gives up and is important for us, but he is suspended so someone else will have to play in his position.

"We hope Ballack can be fit for the game. I saw him running already."

Grant has been very sympathetic to Lampard's personal situation and it is not known when the England midfielder will be available again. But Carvalho believes his team have already proven their ability to cope, having shown strength of character to get back in the title race.

Chelsea are now only two points behind leaders Manchester United who they meet at Stamford Bridge in eight days time. Sir Alex Ferguson's side travel to Blackburn tomorrow when the Blues will be hoping for a favour from the side managed by their former striker Mark Hughes.

Carvalho said: "It was a very important win, we were five points behind Manchester United and knew we had to do our job. Now we have to wait to see what they do. We knew we couldn't make a mistake against Everton and had to win, we have done that and now the gap is only two points. The pressure is back on them.

"We will have to beat them as well, but we will have to see first how they get on against Blackburn on Saturday. Blackburn away is always difficult.

"We showed a lot of character and showed how strong we are after drawing against Wigan. This was a crucial game for us.

"We knew we couldn't draw or lose again. We have to win every game.

"It will be difficult for us to win the league but it is still possible. But we will never give up and it is important we beat Manchester United, even though that will be hard."

The Portuguese international defender is now fully focussed on beating Liverpool in the semi-final of the Champion League.

He has played in both of Chelsea's defeats to Rafael Benitez's men at the same stage twice in the last three years.

He said: "The Champions League is very important for us and has been since I joined the club.

"The first leg at Anfield will be crucial and I hope the luck is on our side this time."