Manchester United will be without defender Rio Ferdinand for the derby against Manchester City on Saturday after he failed to recover from a calf injury.
"He (Ferdinand) will be out for a couple of weeks, Jonny Evans got injured training with (Northern) Ireland so he's out, so young Chris Smalling will play tomorrow," manager Sir Alex Ferguson told a news conference.
"Tomorrow could be a decisive game in terms of the championship for both teams and it makes it an interesting game for us," the Scot added.
Leaders United are five points ahead of third-placed City with a game in hand before the clash at Old Trafford.
City could be boosted by the return of striker Mario Balotelli who is pushing for a place in the squad after being sidelined for a month with a knee injury.
"I will decide if he can go on the bench. If he is not fit, maybe he will need another week," manager Roberto Mancini said.
Netherlands midfielder Nigel de Jong is still a doubt with an ankle injury having missed last Saturday's 3-0 win over West Bromwich Albion and a midweek international friendly.
Arsenal's Swiss defender Johan Djourou is fit to face Wolverhampton Wanderers on Saturday after recovering from a knee injury suffered at Newcastle United last week.
Denilson (hamstring) is also available and fellow midfielder Alex Song (thigh) may be in contention while Robin van Persie and Cesc Fabregas have recovered from sickness.
However, Tomas Rosicky misses out after picking up a groin injury playing for Czech Republic in midweek and Samir Nasri (hamstring) is still not ready for action.
"Samir is continuing his progress. It is difficult to assess. He should be fit to be competitive in one week," said manager Arsene Wenger.
Tottenham Hotspur will be without three key midfield players - Rafael van der Vaart, Luka Modric and Gareth Bale - for Saturday's trip to Sunderland as the London club continue to battle for a top four place.
"We have got to focus on (securing) a Champions League spot. It will be tougher than last year to get in the top four but we've got a chance," manager Harry Redknapp said of his Spurs team who are level on points with fourth-placed Chelsea.
Dutchman Van der Vaart has failed to recover from a calf injury that saw him substituted at halftime against Bolton Wanderers last week. Modric has only recently had his appendix removed while Bale has been troubled by a back complaint.
Long-term injury absentee Jonathan Woodgate is again in the squad after coming through a training match against Queens Park Rangers in midweek without any problems.
Chelsea manager Carlo Ancelotti is likely to continue with Fernando Torres and Didier Drogba up front in the West London derby against Fulham on Monday.
"My aim as a coach is to try to find the better solut
