Ancelotti: We must seize the moment
The Blues were in danger of failing to finish in the top four at the end of February and were 15 points behind and 1-0 down to United at Stamford Bridge on March 1. But their fightback to win that game sparked a run that has seen them take 25 of the last 27 points on offer, slowly reeling in Sir Alex Ferguson's men.
Asked what the key was to winning against their title rivals, Blues boss Ancelotti said: "The moment. You need to use character and personality to play this match. Both teams have that, but it is the momentum."
The force certainly seems to be with Ancelotti's men, who beat Tottenham 2-1 on Saturday thanks to two goals that should not have stood before watching United lose 1-0 at Arsenal after they were denied what appeared a clear penalty.
Sunday's game is nevertheless too close to call, with Chelsea having won at Old Trafford last season in what proved a title decider as well as coming out on top at Stamford Bridge in March.
They have since lost home and away to United in the Champions League, although they are arguably in better form now than they were at the start of last month.
Ancelotti, who revealed his players "spirit" had also improved since their European exit, said: "It is the best moment to play there because now our condition is good and the momentum is also.
"But obviously it will not be easy to play there. I don't think we are better (than United). I think we have the same power, the same strength, the same ability."
Incredibly, retaining the title might not be enough for Ancelotti to keep his job, so he was understandably coy about debating if it would be the most satisfying trophy he had ever won.
"Football is strange," he said. "If it happens, it will be really strange."
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