A late equaliser by Gylfi Sigurdsson denied Manchester United the chance to move up into third place and boosted Swansea's chances of escaping the drop in a 1-1 draw at Old Trafford.
United had taken the lead on the stroke of half-time with a controversial penalty but Sigurdsson struck for a share of the spoils with 11 minutes remaining.
In addition to the frustration of dropping crucial points in the race for the top four, the home side suffered yet more injury problems as defenders Luke Shaw and Eric Bailly limped off.
Swansea produced the first effort of the afternoon when, with six minutes played, Kyle Naughton created the space for Ki Sung-Yeung to fire in an angled shot that cleared David De Gea's crossbar.
United's first injury blow arrived after only nine minutes when Shaw looked to have taken a knock to the ankle and made his way to the touchline before being replaced by Antonio Valencia.
Swansea continued to threaten against their reorganised opponents and Stephen Kingsley crossed low to force Bailly into defensive action.
And with 12 minutes gone, another Bailly clearance crashed off Sigurdsson and bounced narrowly wide of the post.
United were struggling, and with 15 minutes played Fernando Llorente got away from Bailly to force a good save from De Gea.
But a couple of minutes later they sprang into action and Antony Martial's pass found Jesse Lingard, who was denied by visiting goalkeeper Lukasz Fabianski.
Wayne Rooney headed over as United continued to try to build momentum, and on the half-hour a strong Martial run and strike forced Fabianski into another smart stop.
But Swansea soon went back on the attack and Jordan Ayew again made De Gea work.
Ander Herrera crossed dangerously from the right as the first half drew to a close after Martial had set him free, but Swansea defenders were in the right place to clear.
But United broke through in contentious fashion in first-half injury time when Rashford went down under a Fabianski challenge and, despite angry Swansea protests, referee Neil Swarbrick pointed to the spot.
They should have doubled that lead moments into the second half when Herrera created a golden chance for Rooney, but his shot crashed against Martial and Swansea survived.
Sigurdsson, though, was always dangerous and produced another cross that gave Llorente a chance to head at goal, only for the effort to fly over.
And United soon had yet another injury problem to worry about when, after 57 minutes, Bailly went down following a challenge with Llorente.
Although he was able to continue for a few moments, he had to be replaced by Matteo Darmian minutes later.
Fabianski denied Martial soon after the hour when the striker fired in a shot that took an awkward deflection before the injury jinx hit Swansea as substitute Jefferson Montero, on for only a few moments, appeared to pull a hamstring and was replaced by Martin Olsson.
As time ticked into the final quarter of an hour, Valencia had an effort beaten away by Fabianski before Sigurdsson fired over after Leroy Fer had teed him up on the edge of the box.
But Sigurdsson made amends in spectacular style after 79 minutes when he curled a superb free kick up, over the wall and into the top corner after Rooney had fouled Olsson just outside the area.
Another Sigurdsson set piece should have brought a late, late Swansea winner -- but the unmarked Llorente, six yards out, failed to make contact and the chance was gone.