Sunderland - David de Gea's cruel 82nd-minute own goal condemned Louis van Gaal's Manchester United to a 2-1 defeat at struggling Sunderland on Saturday that compromised their hopes of Champions League.
Bidding to close the six-point gap separating them from fourth-place Manchester City, United fell behind in the third minute when Wahbi Khazri's free-kick from out on the left eluded everyone and crept in at the far post.
Anthony Martial equalised in the 39th minute, but Sunderland took the points when Martial's attempt to clear Lamine Kone's header off the line struck goalkeeper De Gea's arm and rolled into the net.
It was United's seventh league defeat of the season and it will only serve to fuel speculation about the position of their manager Van Gaal, amid reports that the club have approached Jose Mourinho to succeed him.
United fell to a first league defeat on Wearside for 19 years and became the first top-half team that struggling Sunderland have beaten this season in 14 attempts.
In their first game since announcing the sacking of Adam Johnson after the England winger admitted to child sex charges, Sunderland took an early lead in fortunate circumstances.
The hosts earned a free-kick near to their left touchline following a foul on Patrick van Aanholt by Matteo Darmian.
Khazri swung in the set-piece, which travelled between the legs of Jermain Defoe, and beyond United's defensive line to find the net off the bottom of De Gea's left-hand post.
Chris Smalling stood firm to prevent Defoe doubling the lead shortly afterwards, shepherding the Sunderland forward's effort to safety after Van Aanholt and Lee Cattermole created a half-chance.
Sunderland's pressure mounted and they had penalty appeals turned down by referee Andre Marriner, who was well placed to wave play on when Khazri's shot struck Morgan Schneiderlin on the arm inside the area.
It took Van Gaal's side half an hour to muster an effort on target, Vito Mannone saving comfortably after Wayne Rooney teed up Mata to send in a tame shot.
It was a warning Sunderland failed to heed, as the visitors drew level six minutes before half-time.
Michael Carrick found Martial down United's left and when his cross was partially cleared by Kone, Mata's low shot from 15 yards was brilliantly saved low to his right by Mannone.
Martial reacted first to chip a superb finish from a narrow angle over the goalkeeper and into the net.
The first half also proved notable for the entrance of Donald Love, who came on for his senior United debut after Darmian injured his shoulder following a collision with impressive home debutant Khazri.
Sunderland had a second unsuccessful penalty appeal early in the second half when the ball struck Rooney's hand as the United captain challenged John O'Shea at the near post at a corner.
The visitors had lost the momentum they were building up towards the end of the first period and it took a fine sliding intervention from Daley Blind to divert Defoe's goal-bound effort from Van Aanholt's cross behind.
The visitors were carved open again soon after, the impressive Cattermole again the source as the midfielder's pass released Dame N'Doye, whose low drive was kept out by the feet of De Gea.
The Spain international then produced a fine finger-tip save to touch a shot from Kone over the crossbar.
The big centre-back was not to be denied for long and he made no mistake when he was afforded the freedom of United's penalty area to meet Khazri's corner with the crashing header that yielded the decisive goal.
United substitute Memphis Depay saw a shot from the edge of the area well saved by Mannone, but Sunderland held on with relative ease for a priceless victory in their quest to avoid relegation.