The boss was delighted with the way his players responded to going 0-1 down to Damien Duff's early strike and swept into a comfortable 3-1 lead at half-time with the threat of more goals to come. But the second half was a let-down by comparison, especially after Fulham reduced the advantage when Matthew Briggs' left-wing cross appeared to be knocked in by Nemanja Vidic. And had David De Gea not denied Bryan Ruiz deep into tense injury time, two points would have been dropped.
"I think we saw the two sides of Manchester United," Sir Alex admitted on MUTV. "After cruise control, we made a terrible mistake for the second goal and it became a match. It should never have been a match, some of our football was fantastic. But we lost that second goal when we should have been in easy street.
"Fulham tried to slow the tempo of the match down. They do it very well because they've got several players over 30 years of age, they're a very experienced team. After their second goal, we struggled."
As for the positives, Sir Alex saw plenty in the opening 45 minutes when home debutants Robin van Persie and Shinji Kagawa - working in tandem with the latter playing off the former Arsenal striker - both scored their first goals for United.
"I was pleased with both of them," said Sir Alex, "It's early doors and they'll have a better understanding as time goes on.
"It's normal for us to play one up front with one in behind, whether it's Wayne who plays in that role or Danny Welbeck. Ashley Young can play there too, Ryan Giggs can... we've got options that way.