Sunderland defender Joel Lynch stretchered from the pitch in Portsmouth defeat
Kenny Jackett’s side produced two set-piece goals either side of the interval to overtake the Black Cats in the table.
Phil Parkinson’s side have dropped out of the play-off spots as their nine-game unbeaten run came to an abrupt end ahead of a crucial game against Ipswich Town at the Stadium of Light next weekend.
There had been little in an open an engaging first half, but Sunderland were desperately poor in the second, unable to string together any passing moves and never threatening to test Portsmouth goalkeeper Alex Bass.
The Black Cats were also left with a major injury concern, with Joel Lynch suffering a serious head injury in the second half that meant the away side had to finish the game with ten.
Lynch was taken straight out of the ground on a stretcher as the game entered the final ten minutes.
The stakes had been high for both sides, in excellent form but knowing that poor results earlier in the season meant that there was little margin for error in the push for automatic promotion.
As such, it was a predictably edgy start, lots of long balls and loose passes as neither side was able to take control of the contest.
Sunderland created the first opening of note, Joel Lynch launching a long ball over the top for Charlie Wyke to gather.
His touch was good and he was able to get a shot away, but it was a relatively comfortable stop for Bass.
Portsmouth responded with an effort of their own, Ronan Curtis whipping an excellent free kick from the left right onto the penalty spot. Ryan Williams got ahead of his marker and flicked a header towards the back post, but it drifted just wide with Jon McLaughlin scrambling across his goal.
Cameron McGeehan flashes a good effort from range just wide, but slowly and surely Sunderland began to take control of the contest and should of scored in a period when they controlled both possession and territory.
Their first clear opening came when Wyke controlled a lofted pass and brought Lynden Gooch into play, the forward finding wing-back Denver Hume.
His low cross was superb, and Chris Maguire had shown excellent awareness to drop into space. He looked set to fire an effort on target, but misjudged the bounce and sliced an effort on his weaker foot straight into the air.
They were beginning to cause serious problems, and came within inches of taking the lead when Luke O’Nien almost fired in the goal of the season.
He found himself under pressure from two defenders but struck a remarkably sweet volley on his left foot, swerving and dipping away from Bass, striking the inside of the past and bouncing back off the goalkeeper as he tried to get up to gather the loose ball.
It somehow dribbled wide of the far post and though Portsmouth’s opener came against the run of play moments later, it came from Sunderland not heeding the warning they had been given earlier in the contest.
Curtis whipped in another excellent free kick from the left, and this time it was Christian Burgess who was free. He made no mistake, nodding his effort past McLaughlin.
Suddenly the Black Cats were on the ropes, and should gave fallen further behind when John Marquis gathered the ball in the box. He had time to compose him but instead snatched at his effort, firing it wide.
The Black Cats began to settle and regain their earlier composure, but were in debt to their goalkeeper who produced a stunning stop. A cross was fired into the box and Wright tried to head clear. His attempted clearance was flying towards goal but McLaughlin, heading in the wrong direction, managed to put out a hand and claw it clear. Portsmouth kept it alive and James Bolton should have scored when the ball fell to him in the box.
Sunderland kept pushing and twice felt they should have had a penalty, first when Chris Maguire felt Ronan Curtis had clipped his heels as he broke into the box. They were then irate when Wyke chased a ball into the box, the Black Cats convinced he was held back as Bass came out to gather.
The referee was unmoved, leaving the Black Cats with much to do at the break.
Wyke had hurt his shoulder in that move, and so Kyle Lafferty was brought on for the second half.
Sunderland started the half slowly, and were punished again when Curtis whipped a superb corner into the box. Bolton, who had missed that glaring opening earlier in the contest, made no mistake this time.
They were fortunate not to fall further behind soon after when Hume lost his man at the back post, Williams teeing up substitute Ellis Harrison who drew another smart stop from McLaughlin.
It was the host side continuing to create all of the chances, Sunderland totally unable to get a foothold into the contest.
Both Williams and Sean Raggett missed good chances to extend the lead further as Kenny Jackett’s side continued to threaten with every set piece.
Parkinson turned to his bench for inspiration, throwing on Duncan Watmore and Antoine Semenyo for his Black Cats debut.
It yielded little, Sunderland still second best.
Harrison had replaced Marquis at the break and alongside Curtis he ran the Sunderland backline ragged.
It had been a tough half for the Black Cats, now left with a major concern over Lynch who had to be taken out of the ground after clashing with his goalkeeper McLaughlin as they tried to clear a ball through the middle.
McLaughlin had to make excellent stops from Harrison and Williams to ensure the lead was not extended further in the closing minutes.
Sunderland XI: McLaughlin; O’Nien, Willis, Wright, Lynch, Hume (Semenyo, 69); Power, Dobson; Gooch, Maguire (Watmore, 69), Wyke (Lafferty, 45)
Subs: Burge, Scowen, Flanagan, McLaughlin
Portsmouth XI: Bass; Bolton, Raggett, Burgess, Seddon; Naylor, Cannon (Close, 90); Williams, McGeehan, Curtis; Marquis (Harrison, 45)
Subs: MacGillivray, Brown, McCrorie, Whatmough, Harness
Bookings: Seddon, 45 Gooch, 45 Dobson, 70 Raggett, 70 Semenyo, 90
Attendance: 18,531 (1,819 away)