Michael Essien's role is so central to success

Since that 2-1 victory over Arsenal on Easter Sunday, Essien has excelled against Middlesbrough, forced Richard Dunne into scoring an own goal at Manchester City, and then netted himself against both Wigan and Everton, all from central midfield.

He was definitely missed at Anfield on Tuesday where the central battle was won by Liverpool, for whom Javier Mascherano was outstanding. The irony is that if he had not been suspended for the Champions League semi-final, second leg Grant would have picked him at right-back anyway as he wanted to play Ballack and Lampard with Makelele in a holding role.

Now, with Lampard so unfortunate to miss out, Essien can slot straight back into the middle.

Mascherano and Xavi Alonso were able to repell Chelsea's midfield at Anfield because their job was to fill the space in front of the back four.

Tomorrow, I have no doubt that Sir Alex Ferguson will do the same with Michael Carrick and Owen Hargreaves.

United are likely to start with a five-man midfield and the return of Nemanja Vidic to central defence will allow Hargreaves - another player who has suffered this season because of his versatility - to move into the middle.

Then with either Paul Scholes or the very impressive Anderson supporting Wayne Rooney in attack, Ferguson's side will be very difficult to break down.

United are not playing particularly well but they are not conceding many goals. Their display in Barcelona was a masterclass in defending - yet the Spaniards failed to press Rio Ferdinand and Wes Brown into any kind of panic measures because their midfielders seemed to be under orders not to break beyond their front three. This is where Essien - as he showed in particular in the 1-0 win over Everton - can come into his own. Chelsea need the victory, so he cannot afford to sit back and Makelele's presence will allow him to roam.

Pride will come into play tomorrow as well. United are travelling to a ground where the Blues haven't lost in 80 League games.

It's difficult to pinpoint exactly why the record is so good. It started with Claudio Ranieri but was taken to a different level by Jose Mourinho. His home record at both Chelsea and Porto was second to none and he instilled the importance of creating an air of invincibility at the Bridge. Grant has embraced that and taken it further.

But it's all about the players. Managers can say what they like before a game and try to alter it with substitutions. But if the players don't have the skill, technique and, more importantly, the willpower and character to refuse to be beaten, then you have no chance.

The Chelsea squad have that in abundance and the unbeaten run is a testament to all the qualities they possess.

Playing against United was always the biggest game for me when I was at Chelsea.

Spurs and Leeds were big games for the supporters but to pit your wits against the best was what it was all about. United were without doubt the team of the nineties. To come up against Eric Cantona, Roy Keane, Ryan Giggs, Paul Scholes and David Beckham was to test yourself to your very limit.

The stakes are a lot higher now and Chelsea will be pushed to their limit tomorrow but, if they are to succeed, then I expect Essien to have a major part to play.