Younes Kaboul was responsible for an extraordinary finish to a match that had seemed certain to end in another defeat for Portmouth.
After 93 minutes of ineptitude from Avram Grant's team, Kaboul moved forward to force in an equaliser that punished Sunderland for their failure to translate possession into clear-cut chances.
Kaboul's celebration was extravagant as he ripped off his shirt to guarantee his dismissal following an earlier caution. For once, though, Grant was not inclined to be critical of his player for such an unnecessary red card.
"It was a silly red card, but it's a silly rule, a stupid rule," he said. "Somebody should explain why it is wrong if he takes his shirt off. One guy at Fifa must have woke up one morning and said that's the new rule. If a player scores in the last minute he needs to control himself, of course, but everybody was happy and celebrating, so he pulled off his shirt – big deal. What is the purpose of the rule? Can somebody explain it?"
And can somebody offer an explanation for how Sunderland failed to win a game which offered plenty of clues to why Portsmouth are at the foot of the table.
Grant's insistence that his team were better in the second half is a valid one, but it was only a marginal improvement, and they failed to create a clear-cut chance until the stoppage- time goal.
Sunderland should have been out of sight long before the interval as Jordan Henderson and Nyron Nosworthy created havoc down Portsmouth's left flank. It was the area that produced their 23rd-minute goal when Henderson's trickery took him past Marc Wilson before he crossed beyond the far post to Andy Reid, who set up Darren Bent for his 10th goal of the season.
Henderson was off-target with two further opportunities, while both Bent and Kenwyne Jones failed to accept second-half opportunities as the tension started to surface in a Sunderland side who were doubtless mindful of the fact that they had lost three of their previous four games without scoring a goal.
A month ago, there was optimistic talk of a challenge for a place in the top six; now Steve Bruce's men are slipping towards the bottom half of the table, although at least they know they are a class apart from this Portsmouth side.
Bruce said afterwards: "We should have been out of sight well before their goal, but how often have we seen that happen when don't get the second goal. It puts everybody on edge in the last four or five minutes.
"We were naive when we gave the ball away, then we were hit with a sucker punch. It's something we didn't deserve, but you have to take your chances."
Referee: Steve Bennett
Man of the match: Nosworthy