Jamal Lowe’s fifth goal of the season was not enough for Swansea City as they suffered defeat to Middlesbrough at the Swansea.com Stadium.
The Swans enjoyed the better of the opening half, with Josh Key, Bashir Humphreys, Jay Fulton and Liam Walsh all having chances, only for Sam Greenwood to put Boro ahead just before half-time.
The hosts responded after the break and deservedly levelled through Lowe’s header, but ended the afternoon on the wrong side of the scoreline when substitute Sammy Silvera netted from an indirect free-kick for the visitors.
It was harsh on caretaker head coach Alan Sheehan and his side. The Irishman had demanded an improved performance and had got one, with the Swans creating plenty of chances and causing the visitors a number of problems, but they were left empty-handed thanks to Silvera's late strike.
The Swans had made two changes from the midweek draw at Stoke as Walsh and Humphreys came in for Charlie Patino and Jerry Yates respectively.
The opening exchanges were scrappy, Carl Rushworth raced off his line to clear away a long ball downfield as Isaiah Jones and Emmanuel Latte Lath closed in, before Harry Darling drilled into the side-netting after beating his man by the right byline.
Key then headed wide from a Walsh cross after drifting infield from the right flank, before Walsh was again prominent as he kept a ball in on the byline and saw Boro skipper Jonny Howson hack his cross clear.
The hosts continued to look the more likely to find an opener, Humphreys glancing a header agonisingly wide from a Walsh delivery 15 minutes in.
The Swans spurned another gilt-edged chance seven minutes later, Matt Grimes sent Lowe into space and the forward’s lay-off found the onrushing Walsh, only for the midfielder to steer his effort wide with the goal at his mercy.
Rushworth parried Greenwood’s effort from a narrow angle round the post at the other end but Swansea were soon back on the front foot, Walsh and Jamie Paterson combining in a move that ended with Dael Fry spooning a clearance over his own bar.
Fulton was next to go close, his outside-of-the-foot effort bouncing narrowly wide of the far post after more neat work by the lively Walsh.
But instead it was the visitors who took the lead two minutes before the break.
Matt Crooks made the goal with a powerful surge and slid the ball through for Greenwood to dispatch a left-footed effort into the bottom corner.
The visitors built on that momentum by making an assured start to the second half, but Paterson lifted a spell of Boro pressure with a surging run and turn before sending an effort wide of the target.
And the Swans levelled two minutes before the hour mark. Josh Tymon was worked into space down the left and Lowe stooped to head home his terrific cross.
Fulton was denied a quick second as Seny Dieng blocked his near-post effort after tremendous link play with Walsh.
Paterson then had penalty appeals waved away after he tumbled under a covering challenge in the area.
It was end-to-end stuff, and Rushworth made a sharp stop as he raced off his line to deny Isaiah Jones, with Fulton blocked Latte Lath’s follow up.
Paterson drilled a ball across the face of goal at the other end as time began to run down for either side to find a winner.
And it was the visitors who snatched the points after Darling’s tackle was adjudged to have been intended as a backpass, which Rushworth subsequently picked up.
Silvera took aim from the indirect free-kick and managed to sneak a low effort into the net off the inside of the left-hand upright.
Tymon forced Dieng - who soon left the field due to injury - into a low save as he raced onto a pass in behind but the Swans could not find a leveller.
Swansea City: Carl Rushworth, Josh Key, Jay Fulton (Charlie Patino 87), Ben Cabango, Harry Darling, Matt Grimes (captain), Jamal Lowe (Liam Cullen 87), Jamie Paterson (Yannick Bolasie 81), Josh Tymon, Liam Walsh (Ollie Cooper 64), Bashir Humphreys (Jerry Yates 81).
Unused Substitutes: Andy Fisher, Nathan Wood, Kyle Naughton, Sam Parker.
Middlesbrough: Seny Dieng (Tom Glover 90), Rav van den Berg, Isaiah Jones, Anfernee Dijksteel, Sam Greenwood (Sammy Silvera 72), Jonny Howson (captain), Dael Fry, Alex Bangura (Lukas Engel 72), Matt Crooks (Morgan Rogers 71), Daniel Barlaser, Emmanuel Latte Lath.
Unused Substitutes: Matt Clarke, Alex Gilbert, Hayden Coulson, Daniel Nkrumah, Calum Kavanagh.
Referee: Matthew Donohue
Attendance: 15,084
