Sunderland turned in an impressive display against the title holders, with Stephane Sessegnon going close to adding to the Black Cats' lead on a number of occasions, with top scorer Steven Fletcher also testing City's resolve. Adam Johnson proved the matchwinner on the day.
"We were committed and had some fantastic touches throughout the game," the manager told safc.com, "We could have scored more goals!
"Everybody worked incredibly hard for the team. Wingers coming back to help full-backs and then full-backs getting forward to cover, it was just brilliant."
O'Neill also paid tribute to the bumper Boxing Day crowd at the Stadium of Light, who gave the players a standing ovation at the final whistle:
"Today the crowd were right behind us from the start and kept with us." O'Neill added.
"It was a great atmosphere."