With United losing three of its last five league matches and Arsenal's injury problems slowing its progress, the door is ajar for Chelsea and City to mount a late challenge.
City is seven points off the lead with nine matches left and Chelsea, which has a game in hand, is two points further back.
Chelsea striker Didier Drogba said his team's title chances are “really, really small” after its mid-season slump, but is ruling nothing out.
“We have to focus on third place, because the club has to be in the Champions League,” said Drogba, who could be paired with recent signing Fernando Torres again this weekend.
“Let's focus on Sunday - it's going to be a big game for us. We'll see what happens three or four games from the end.” The visitors will hope that playing almost an hour with 10 men in Thursday's 1-0 win over Dynamo Kiev in the Europa League - which wasn't enough to send them through to the quarterfinals - doesn't return to haunt them, with their first-choice team looking jaded by the end of the match.
Italy striker Mario Balotelli, red-carded in that victory for a petulant studs-first lunge in the 36th minute, is set to be dropped by City manager Roberto Mancini.
“I don't think he'll be in the squad,” Mancini said.
“Mario thinks he could be a fantastic player. When he does something stupid like that, it's difficult for me.” Torres is yet to score for Chelsea since his 50-million-pounds ($81 million) move from Liverpool but after being a substitute in the 0-0 draw against FC Copenhagen on Wednesday, the Spain striker will be raring to go.
Torres is also keen to make his partnership with Drogba work, although manager Carlo Ancelotti could opt to play Nicolas Anelka instead of the Ivory Coast international.
“I think we are mature enough and clever enough to play together,” Torres said of Drogba. “There's no question about this.” United will look to extend its unbeaten record at home this season when it hosts Bolton on Saturday but the leaders are without at least four injured defenders, including the first-choice center-back pairing of Rio Ferdinand and Nemanja Vidic, who have hamstring injuries.
That gives in-form Bolton, which is in seventh place, a chance of a first win at Old Trafford in nine years.
“As a player, coach or manager, you want to play against the best. And it doesn't come any better than Manchester United, with the best manager in world football bar none,” Bolton manager Owen Coyle said.
“Sir Alex (Ferguson) knows the way my teams play, and we'll have to be at our best to achieve something.” Arsenal is without a win in its last four away matches in all competitions ahead of its trip to fifth-bottom West Bromwich Albion, which earned a first victory under new manager Roy Hodgson when it beat Birmingham 3-1 last time out.
Fifth-place Tottenham, the other team with an outside chance of catching the top two, is at home on Saturday to West Ham, which has been revitalized by the January signing of striker Demba Ba and the return to fitness of Germany midfielder Thomas Hitzlsperger.
West Ham is still in the relegation zone but has won its last two league games.
Elsewhere Saturday, Aston Villa hosts second-bottom Wolverhampton Wanderers in a midlands derby, Blackburn is at home to fellow strugglers Blackpool, Newcastle visits Stoke, Birmingham travels to last-place Wigan and resurgent Fulham goes to Everton.
Liverpool manager Kenny Dalglish could pair expensive January signings Luis Suarez and Andy Carroll up front together for the first time when the northwest side visits Sunderland.
Sixth-place Liverpool, which is six points behind Tottenham having played a game more needs to finish fifth to make it into European competition next season.
