United took three points to go back to the top of the table but were made to fight all the way by obdurate Fulham, who defended manfully throughout and ensured a nervous night at Old Trafford.
Wayne Rooney's first-half strike proved just about enough but Sir Alex's side were unable to add to the goal and the atmosphere grew increasingly tense in the closing stages with Danny Murphy, so often the scourge of United in the past, perhaps unlucky not to earn a penalty after going down inside the area towards the end.
Although the Reds dominated the early exchanges, the first genuine effort did not arrive until the 11th minute when Ryan Giggs met a Rafael cross with a goalbound header but Mark Schwarzer caught it impressively. With Giggs being asked to play the Paul Scholes role in his fellow veteran's absence, his probing passes were regularly dealt with by the Cottagers' defence.
Gradually, Fulham came more into the game and Moussa Dembele's menacing dribble led to him dragging a shot wide before Clint Dempsey ran at Jonny Evans but shot too close to David De Gea. The Londoners continued to put their bodies on the line at the other end, making a series of fine blocks, and, with the team growing in confidence, Dempsey forced a spectacular diving catch out of De Gea.
Predictably, the Reds responded to the wake-up call through Antonio Valencia but his shot was blocked by John Arne Riise after a one-two with Danny Welbeck. The breakthrough was almost provided by an unlikely source when Patrice Evra's ambitious overhead kick dropped wide and fellow full-back Rafael also had a decent chance but shot tamely at Schwarzer with his left foot.