The Black Cats took the lead through a first-half striker Darren Bent, but Pompey managed to get a draw in stoppage time after a goal by Younes Kaboul.
Bruce admits the draw felt like a defeat.
“We were guarding against the equaliser for the last five minutes but the disappointment for me is that we were not out of sight well before then and when you don’t get the second one how often have you seen something like that happen?” said Bruce.
“You get hit back by a sucker punch like that and it is something I don’t believe we deserved but you have got to take your chances.
“I think to play here in front of a big expectant crowd you have to have a certain mentality and we have to be bigger than the expectations, you have to be able to take the ball down and be confident, of course if we don’t get results pressure will come but this is the Premier League.
“I don’t know how many shots we have had but we have certainly had enough to win and it feels like a defeat for us, the players, the fans – everyone involved at the club.”
He continued on Kaboul’s goal: “The corner only came in at head height, we should be disciplined enough to get that away – it was a pinball when it went in, but we should have cleared it.
“My biggest disappointment is that we didn’t hold the ball like we are capable of and we invited the pressure. I don’t think Portsmouth threatened us in front of goal but we just invited them on by giving them the ball constantly.
“Today would have been a great lift for us considering the injuries and suspensions, but this is the Premier League, this is what it is about. We are up against it and this is where we have to earn our money.
“We have had a good start and we go into Christmas in tenth and we certainly could have had more points than we do have.”
