O'Neill had no complaints at the final whistle, instead heaping praise on the quality of the City side.
"Eventually over the piece Man City deserved to win. When it was 1-0 we had a chance and just after the break we had an attacking threat, but overall they were much better and deserved to win the game," said the Sunderland boss.
"They were electric. They are fine players, champions of this country and playing big Champions League games. It was always the possibility if they got the second goal, they would cause havoc and that happened. If another 10 minutes went by they might get a bit nervy.
"You just have to take it, wait for international players came back and then prepare ourselves for Newcastle."
The win lifts City up to second in the Premier League table.