The former United icon saw his resilient Black Cats lose narrowly against the Premiership champions thanks to a 72nd minute striker from Louis Saha, but apart from the result, Keano was glad to be back.
"I have to say the reception I got from the United fans was fantastic, they've always been great to me and I appreciate that very much," he told Setanta Sports.
"It's small consolation at this moment in time because we lost the game. Nevertheless I'm very grateful because they've always given me nothing but great support."
On the other hand, United manager Alex Ferguson hailed his goal hero Saha after the Frenchman marked his return from long-term injury with the crucial winner.
"Louis Saha made the obvious difference when he came on, he gave us strength and penetration and he got us the goal. I didn't want to start with him but at half-time I thought he was needed," Ferguson was quoted as saying by Sky Sports.
"He is different from the rest of our players and, for the first time, they looked pretty edgy at the back."