London: Manchester United hope to strike a major Boxing Day blow as the Premier League title race enters its most hectic period of the season on Sunday.
United head into the latest round of fixtures at the top of the table with Sir Alex Ferguson`s men, who have a game in hand, two points clear of Arsenal and Manchester City, with champions Chelsea a further point adrift in fourth place.
United have yet to lose in the league this season, having won nine and drawn seven of their 16 matches.
They welcome a Sunderland side managed by former United captain Steve Bruce to Old Trafford on Sunday knowing the Black Cats have already won at Chelsea this term.
"Someone asked me `are you surprised to be top of the league?," said Ferguson. "I`m only surprised that people are surprised all the top teams are dropping points."
"They don`t recognise how tough the league is now."
Victory for United would enable them to go five points in front of Arsenal before the Gunners face Chelsea, who have gone five games without a win, in an all-London clash on Monday.
Blues manager Carlo Ancelotti would love nothing more than for his side to extend Arsenal`s winless run against Chelsea and United to 12 matches in total.
"Manchester United are having fantastic results because they`ve not lost a game, they`re continuously obtaining results," said Ancelotti.
"We don`t want that gap to widen. So it`s important to obtain an important result in this game. We have to do our best to take three points against Arsenal, and the same against Bolton and Aston Villa."
Postponements brought about by the cold snap in Britain have left Chelsea without a game for more than two weeks but striker Didier Drogba will certainly fancy his chances on Monday after scoring 13 goals in 13 games against Arsenal.
"I think they are a little bit afraid of the performance of Drogba because he has done very well against them," Ancelotti said.
"This is not the reason that will decide the game but if Drogba plays at his best, we`ll have more opportunity to win."
Arsenal manager Arsene Wenger made no attempt to disguise the enormity of the clash, saying: "Of course this is a must-win game."
"We have mixed feelings because we came out of both games against Chelsea and Man United this season thinking we could have won and that there wasn`t a difference between the teams."
Another London derby could have a key bearing on the relegation race with Fulham, above the drop zone on goal difference alone, facing bottom of the table West Ham -- currently three points behind the Cottagers.
Fulham manager Mark Hughes played down suggestions defeat by the Hammers would lead to the sack.
"There will be speculation, there always is," Hughes said. "There is nothing I can do about it."
"I don`t particularly feel under pressure. I`ve been through this before," the former Blackburn and Manchester City boss added.
Wolves face Wigan in a relegation zone dogfight while, at the top of the table, Manchester City will look to maintain their title bid away to Newcastle.