Kalou, who opened the scoring for the Blues in Saturday's disappointing 1-1 FA Cup third-round draw with Coca-Cola League One Southend, insists they must keep Sir Alex Ferguson's champions behind them in the title race.

"This game is crucial because if they win on Sunday they have the chance to build a lead over us as they have two games in hand as well," said Kalou.

"It is important to keep the gap because if you allow United to get in front it's always difficult to catch them.

"Last year we were always running after them and so far this season they have been the ones behind us - we want to keep it that way.

"We are still hoping to win the title and we are going to Manchester to show them that we are still Chelsea and we want to win the League.

"People on the outside seem to think it's all doom and gloom here at the moment but we are still second in the League, we are still in the FA Cup and Champions League.

"I don't think we are underperforming. We have had some bad results but that happens at a big club, you can have moments when you don't do well."

Following their trip to Old Trafford, Chelsea travel to Roots Hall to face Southend in their third-round replay.

Coach Luiz Felipe Scolari blamed his side's lack of cutting edge for not finishing off Steve Tilson's side before Peter Clarke stooped to head a shock equaliser in the 90th minute, and Kalou agrees they should have put the game beyond the Shrimpers.

"If you score the first goal and you don't then kill the opponent, they can always come back and that is what happened against Burnley (in the Carling Cup) and that is what happened in this game as well," said Kalou

"They pressed well and they tried to put us in trouble and that is what they did. Of course when you have the opportunity to kill the game and go to the next round and you draw at home, it is never a good result so everyone is a bit frustrated.

"Now we have the match there and we have to go there and do better. It will be a difficult game away because they will be pushed by their fans, but I am confident that we can go there and beat them so we have to be really focused - but the most important, first, is Manchester next Sunday.

"I have not been playing for a while so for me to start was nice and to score has given me more confidence. I hope that I will get more opportunities to play."