For a club cruising to a record 20th English league success, Manchester United faces a curiously unfulfilling end to the season.

Sitting 15 points clear in the Premier League, United's victory in the title race seems a formality, but disappointments in the Champions League and FA Cup have left a mark.

Before the Champions League last-16 second-leg with Real Madrid, talk was rife of United repeating its historic 1999 treble of league, cup and European Cup trophies.

Twenty-eight days later, such thoughts have vanished, with Madrid having prevailed in the European tie before United fell to Chelsea in its FA Cup quarterfinal replay on Monday.

United's fans had hoped the season would culminate with three trips to Wembley, for the FA Cup semifinal and final, followed by the Champions League decider on May 25.

Instead, they find themselves confronted by the comparatively mundane prospect of a league campaign that is still almost seven weeks from its conclusion.

The balance of United's encounter with Madrid hinged on the controversial dismissal of Nani in the second leg in Manchester on March 5 and in hindsight, it may have been the moment that its season petered out.

Madrid swiftly exploited Nani's dismissal - for a high challenge on Alvaro Arbeloa - to turn around a 2-1 aggregate deficit, and there has been an air of resignation around Old Trafford since.

Alex Ferguson's side went 2-0 up in its next match, against Chelsea, but its performance was careless and Rafael Benitez's side stormed back in the second half to take the tie to a replay.

Since then, United has produced two labored 1-0 wins, at home to Reading and away to Sunderland, which preserved its commanding lead at the top of the league table but did little to quicken the pulse.

It toiled at Chelsea on Monday, too, threatening only sporadically and failing to rouse itself for the kind of last-ditch assault that is the club's calling card.

Saturday's 1-0 win at Sunderland was United's 15th victory by a one-goal margin in the league this season, one game short of the record it set en route to the Premier League title in 2009.

For all the goals it has scored, United has rarely been ruthless, and it is on course to finish the league season without having put five goals past an opposing team for the first time since 2006.

The theory of a malaise is given weight by the diminishing returns of strikers Robin van Persie and Wayne Rooney.

Van Persie made an explosive start to his United career, netting 22 goals by mid-January, but since then he has scored just once and has now gone nine games without finding the net for his club.

Rooney, who has missed the past two games through injury, has also experienced an indifferent campaign, and had to contend with speculation about his future after being left on the bench for the visit of Madrid.

United will have plenty of time to stew over its cup elimination by Chelsea, as it is not in action again until Manchester City visits Old Trafford in the Manchester derby next Monday.