Chelsea are determined to bring Manchester United's electrifying start to the season to a juddering halt on Sunday as the Premier League rivals collide in a heavyweight clash at Old Trafford.

The Londoners travel to Manchester as underdogs having already suffered three crucial defeats against Sir Alex Ferguson's men this year, losing in both the league and Champions League at the tail-end of last season.

Chelsea manager Andre Villas-Boas admits Didier Drogba is set to miss Sunday's clash as the Ivory Coast striker continues to recover from concussion.

Drogba was concussed in a collision with Norwich goalkeeper John Ruddy during Chelsea's 3-1 victory on August 27 and has yet to return to action.

The 33-year-old resumed full training with Chelsea's first team squad on Friday, but Villas-Boas believes the trip to Old Trafford had come a week too soon for Drogba.

As if their poor recent record wasn't daunting enough, Chelsea are also facing a United side who have started the season in dazzling form, racking up four consecutive wins and notching an unprecedented 18 goals.

Chelsea know only too well however that early season appearances can be misleading, pointing to the club's blistering start last year, when they notched 17 goals in four wins before enduring a slump which scuppered their challenge.

"United started very well this season but, if you remember, we started last season the same," Chelsea defender Branislav Ivanovic said.

"They've improved as a group but we have our aim, we have our idea and we try to use this on the pitch. "It's going to be the hardest game for us until now and we have to show more than 100% of our power."

Ivanovic played in all three of the defeats suffered by Chelsea against United last season, which included two comprehensive losses in Manchester.

No mind games from Chelsea manager

Chelsea manager Andre Villas-Boas insists he has no intention of playing mind games with Sir Alex Ferguson and the rest of the Premier League's top bosses.

Villas-Boas' mentor Mourinho relished the opportunity to wind up rival bosses like Rafael Benitez and Arsene Wenger and occasionally took a swipe at Ferguson, although their relationship was generally cordial.

Whereas Mourinho felt the match began with his press conferences, with his waspish comments aimed at taking the attention off his players while also irritating opponents, Villas-Boas prefers to keep the peace whenever possible.

"I don't see any reason to play mind games," he said. "If you react to things people say it might look as if you are vulnerable to pressure.

"That is why I took care in reading Ferguson's full press conference before this match. I knew what he said before I came here (to speak to the press) and he didn't say anything disrespectful."

Blues strongest challenger: Ferguson

Sir Alex Ferguson believes Chelsea still represent one of Manchester United's sternest challengers for the Premier League despite manager Andre Villas-Boas's relative lack of experience.

The spotlight has been off Chelsea, who have been challengers for the last seven years, and switched closer to home with Manchester City joining near-neighbours United at the top of the Premier League.

But Ferguson says the focus and publicity being away from the Londoners will suit Villas-Boas down to the ground.

The top-flight’s youngest coach would have been boosted by the settling in period as he finds his feet in his new home.

And although the 33-year-old former Porto manager faces his biggest challenge yet when he faces Ferguson on Sunday, the Manchester United manager anticipates his side will still be taking on one of their biggest rivals to their crown.

"They will be there at the end of the season, there is no doubt about that," Ferguson said.