Although they created little in the way of chances, Sunderland chased and harried a Red Devils team still well short of the form that won them the Premier League title last season.
Keane was lauded as a hero by the United fans, who worshipped him during his 12 successful years as a player at Old Trafford, while the manager's name was rarely off the lips of the Sunderland fans.
But it was a man feeling his way back from injury for United who proved a real hero of Old Trafford.
After lacklustre first half in which United had about as much bite as a toothless bulldog, Louis Saha stepped off the bench and into the scorebook.
A half-time replacement for Anderson - making his Premier League debut after a £13.2million summer move from Portuguese side FC Porto - Saha struck with the only goal of the game in the 72nd minute.
Nani swung over his corner from the left and Saha sneaked in between Dickson Etuhu and substitute Daryl Murphy on the near post to nod the ball beyond Sunderland goalkeeper Craig Gordon and into the net.
Scotland goalkeeper Gordon had an outstanding game for Sunderland as did deadline day buy Danny Higginbotham - a former United player.
Gordon denied United several times with his best save coming from Saha in the 57th minute.
Owen Hargreaves and Chris Eagles carved an opening for the Frenchman, who brilliantly brought the ball down over his shoulder before hitting a blistering 25-yard dipping volley which was superbly turned behind by Gordon.
United's only first-half threat came in the last ten minutes of the period.
Anderson's cross-field pass set-up Carlos Tevez on the left side of the Sunderland box and the Argentinian's shot from 12 yards was well saved by Gordon at full stretch.
Gordon kept out Nani's 25-yard drive after he had worked a fine one-two with Eagles, while Paul Scholes twice went close with shots in the closing seconds of the half.
Sunderland's only real threat came from a half-chance which fell to new signing from Southampton Kenwyne Jones on the hour, but United goalkeeper Edwin Van der Sar was alert to clear the danger.