The Ivory Coast international was controversially dismissed after 25 minutes following a tackle on Sunderland forward Steven Fletcher and, despite playing against 10 men for more than an hour, it took the Black Cats until the 85th minute to draw level when Demba Ba put the ball past his own goalkeeper.
The Mapgies scored in just the third minute through French midfielder Yohan Cabaye and O'Neill suggested that the visitors having a score to defend may have made his players' job tougher.
"Newcastle were strong, they played to their strengths and it was the sending-off that gave us the opportunity to press," the Northern Irishman told reporters after the game.
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"In the second half I think pressure alone yielded us the goal rather than anything else. We got the goal and maybe had a bit more time to go on to win it but, in the circumstances, with Newcastle going down to 10 men and defending so strongly, that would have been harsh."
Sunday's Tyne-Wear derby at the Stadium of Light was O'Neill's first home experience of a North-East derby at Sunderland's home after a bitter encounter at St James' Park last season - and he conceded that the sheer intensity of the atmosphere took him aback.
"I must admit it was a genuine experience for me," the Black Cats manager addded. "The noise that greeted kick-off was just awesome and the noise that greeted our equalising goal is something I won't forget in a hurry.
"It was a tough home game but I felt our creative players are just finding it a bit tough at this moment. They need to get back to what they are capable of doing and we'll be OK. Taking everything into consideration, getting that late equaliser has definitely kept spirits up.
"If we're chasing the game, I won't be taking off creative players. We have enough players capable of making something.
"We were pressing forward and Newcastle were hanging on and I thought we just might be able to thread something through. if we're chasing the game, then I'm not inclined to take players off. There was a little bit of tiredness creeping in [in the case of Stephane Sessegnon]."
|"I have faith in the lads. We didn't get beaten in that game and I have a feeling that may be a valuable point"
- Martin O'Neill
Sunderland have drawn five of their seven Premier League matches this season, with their only defeat coming at Manchester City, and O'Neill insists that he is not getting worried about his side's inability to win games.
"I have faith in the lads," he declared. "We didn't get beaten in the game and I have a feeling that may be a valuable point.
"Obviously would have liked to have converted one or two of them to wins but we've had tough games. I suppose, if there is any regret over the games we've played, I'd say not holding on at West Ham for these two extra points."