And the Irishman looked set to take a point back to Sunderland as an added momento of the day until Louis Saha, a half-time replacement for Brazilian new-boy Anderson, glanced home Nani's corner 19 minutes from time to score his first Barclays Premier League goal since December and ensure United did not lose any more ground in the title race.
It was a gut-wrenching blow for Keane, although the Black Cats boss admitted Saha's introduction changed the game in his old club's favour and they had been given a warning just before the Frenchman's matchwinner when Nemanja Vidic fired over from a similar position.
Still, Keane was not dispirited enough to turn down his old boss, Sir Alex Ferguson, after the final whistle.
"He has asked me in for a drink and I will go," he said.
"What happens at Manchester United is none of my business. I am sure they will be all right but the result probably overshadowed the day.
"I didn't really get sucked into it or bogged down by the fact I was coming back.
"I appreciated the reception. The United fans have always been good to me, even when I let the club down when I was a player.
"But I am disappointed by the defeat because I felt we could get a positive result."