Chelsea were the first big-four side to score on Boxing Day, taking the lead after just three minutes against West Bromwich Albion through Didier Drogba.
Nicolas Anelka then added another goal for good measure on the brink of half-time, to see the Blues through to a first win in three league games and maintain their six-point lead over United.
Liverpool also returned to winning ways, blowing away Bolton 3-0 at Anfield with goals from Albert Riera in the first period and two from Robbie Keane in a five-minute spell shortly after half-time.
Harry Redknapp's Tottenham were held 0-0 at home by Fulham - meanwhile the meeting of Harry's two former clubs in the Barclays Premier League brought a big away win for West Ham, 4-1, at Portsmouth. Algerian defender Nadir Belhadj gave Pompey the lead but after Jack Collison equalised, the Hammers went on to win convincingly with two goals from Spurs transfer target Craig Bellamy and one from Carlton Cole.
Manchester City went one better, battering Hull 5-1 at Eastlands. There was a first-half brace apiece for Caicedo and Robinho, then Ireland capped the Christmas romp in the 83rd minute, just after Fagan hit Hull's consolation.
United's next league opponents Middlesbrough lost 0-1 at home by Everton, after conceding Tim Cahill's goal early