The Black Cats have now taken just three points from their last seven games and remain in relegation danger with fixtures against Manchester United, Chelsea and Newcastle on the horizon.
They failed to truly trouble Norwich on Sunday afternoon despite playing an hour with a man extra when Canaries goalkeeper Mark Bunn was issued with a red card by referee Chris Foy for handling outside the box.
Wes Hoolahan had given the visitors the lead prior to that, with Sunderland levelling from the spot through Craig Gardner after Sebastien Bassong saw the ball roll down his arm, while Danny Rose only conceded a free-kick on the line despite handling inside the area.
O'Neill told Sky Sports: "I thought the sending off looked a sending off at the time because it seemed to follow the rules.
"Norwich will be disappointed, obviously, because that might turn the game a little bit.
"We might have got a little bit of luck as Danny Rose's handball might have been in the penalty area.
"Not that we deserved much luck today, but there have been about seven penalty decisions which have gone against us in recent times.
"So perhaps that little bit of luck that we may not have deserved may have been due in our direction."