The Black Cats could have secured their top-flight status with a win and they took the lead with a 59th-minute opener from Kenwyne Jones.
But Portsmouth scored twice inside seven minutes through John Utaka and Phil Bardsley’s own goal after a dreadful gaffe from Anton Ferdinand, before an Armand Traore strike sealed victory three minutes from time.
“Anton’s obviously held up his hand,” Sbragia said, reflecting on the second goal. “It’s happening too often in general – we play well, we think we’re sort of in charge of the game.
“We knew in the second half they’d push on to us and close us down. but we got off to a good start. Kenwyne scored and from then on we should have been a bit more confident and bossed the game.
“We kept the lead for two minutes, and that’s not acceptable. The second goal was a bad mistake by Anton. He switched off. I would imagine he should have just put his foot through it and helped it on.
“From then on I thought we played reasonably well. We left ourselves open late on – we were obviously trying to go for the equaliser.”
Sunderland had their chances, but could not add to their solitary strike from Jones.
“It’s disappointing, although I thought we created a few chances in the first half but it’s the same old story – not clinical enough,” said Sbragia.
“We let them off the hook. When I thought we were reasonably on top they go one up. Their first goal was obviously a bit unlucky as it’s come off Grant (Leadbitter) but the second goal was the killer for us today.
“I thought we marched on. Kenwyne had a chance, Kieron (Richardson) had a chance but he went for power. Sometimes I think it’d be nice to take the chances we create.”
Sbragia was shown replays of the Pompey equaliser, when Peter Crouch’s header ricocheted off Grant Leadbitter back into his own box and Utaka held off Sol Campbell to turn and rifle home his first goal of the season.
The referee appeared to blow his whistle for a foul just before the ball was struck, but then played the advantage as Utaka netted.
But Sbragia refused to criticise the decision, saying: “I didn’t realise that. He’s probably blown a wee bit early and plays the advantage.
“I’ve got too many other things to think about. Whether it’s a mistake or not, he’s given a goal. I’d have felt hard done by if I was Portsmouth.”
Portsmouth were already safe after weekend results went their way but it was they who set the early pace.
But the match really lit up after 59 minutes when Jones, a constant thorn in Portsmouth’s side whenever they managed to get him involved, finished a swift counter-attack.
But at the other end, Crouch’s header ricocheted off Leadbitter back into his own box and Utaka held off Campbell to turn and rifle his first goal of the season past Fulop.
And seven minutes later Sunderland were behind after Ferdinand’s howler allowed Utaka to steal into the box again. Utaka dragged the ball past Fulop and full-back Phil Bardsley’s flying challenge only succeeded in turning the ball into his own net.
Portsmouth wrapped it up with three minutes left after Traore was given too much time to pick his spot.
PORTSMOUTH: Begovic, Johnson, Campbell, Distin, Hreidarsson, Utaka, Davis, Mullins, Hughes (Traore 46), Kanu (Kaboul 46), Crouch (Primus 90).
SUNDERLAND: Fulop, Bardsley, Davenport, Ferdinand, Collins, Tainio (Cisse 80), Malbranque (Edwards 54), Whitehead, Leadbitter (Murphy 85), Richardson, Jones.
Referee: Alan Wiley.