WIGAN Athletic twice took the lead but couldn’t hold on and saw their Premier League survival hopes suffer a crushing blow at the DW Stadium.
Roger Espinoza gave the home side the lead on the stroke of half-time, but Angel Rangel equalised within three minutes of the restart with a crisp volley.
James McCarthy’s drive put Latics 2-1 ahead shortly after, but again they couldn’t build on the lead and an error from Gary Caldwell allowed Itay Shechter to level.
And with Latics pushing forward for a third goal, they were caught napping as Dwight Tiendalli took advantage of more misunderstanding at the back to fire a scrappy winner.
It leaves Latics three points adrift of safety with just two matches remaining, with a trip to Arsenal and a home game with Aston Villa to come.
Roberto Martinez had made three changes to the side that started at West Brom, Caldwell in for Ronnie Stam, James McArthur for Jordi Gomez and Espinoza replacing the injured Jean Beausejour.
And with so much at stake, it was perhaps understandable that the home side made a somewhat nervous start.
A slip from Paul Scharner allowed Wayne Routledge in, which forced a good save by Joel Robles at his near post.
The resulting corner was stabbed just wide at the near post, and the home support did their best to put their favourites at ease.
Quick feet by Callum McManaman bamboozled Swansea left-back Ben Davies, although the winger wanted one turn too many and he ran the ball out of play.
Arouna Kone was rather more direct with his first sight of goal, and his shot was well saved by Michel Vorm at his near post.
Tiendalli then made his way to the byline after a one-two with Routledge, although his pull-back was kicked away to safety by Joel.
There was a major scare for Latics on 18 minutes when Caldwell steered the ball back to Joel, who picked it up without thought.
Referee Kevin Friend immediately whistled for a deliberate backpass, and the Swans had a free-kick eight yards from goal.
Ashley Williams put everything he had behind the shot, but his aim was off and the ball flew into the fans in the South Stand.
Latics were trying to get McManaman into the game as often as possible, Caldwell finding him on one occasion with a raking crossfield ball.
But the home defence were alert to the danger, and were double-teaming him at every opportunity.
A left-footed effort by McCarthy was deflected just wide, with Shaun Maloney’s corner finding Scharner.
The Austrian’s header was blocked, and Swansea had another escape when Kone’s cross appeared to hit hand of a defender only for Friend to wave play on.
Great skills from McManaman then took him past Davies again and, although his cross was over-hit, it was a positive sign.
Latics came close to a breakthrough when Kone got free down the right, but his drilled effort was well saved by the legs of Vorm.
The home side were enjoying plenty of possession which kept being foiled by poor touches and bad decision-making.
And Swansea were looking increasingly dangerous on the break.
Maloney was fouled by Rangel on the edge of the area as Latics pushed forward with purpose, but his free-kick was 20 yards was straight at Vorm.
Shechter had a shot blocked by Scharner and, in his attempt to win the ball back from Espinoza, conceded the foul and a booking.
And with referee Friend having signalled one additional minute, Latics took the lead with the final play of the first half.
The ball came in from the right, Kone challenged with Vorm, and the ball looped towards the edge of the penalty area.
Espinoza steadied himself before aiming a left-foot volley that flew in at the near post.
The home fans were still cheering as the half-time whistle sounded, but everyone inside realised the job was only half-done.
That point was proved within moments of the restart, with the Swans coming flying out of the blocks.
A short corner got Leon Britton free, and McArthur did well to block his shot.
Another clever opening saw the ball arrive at Tiendalli, but his volley was way off target.
But the goal was coming, and it duly came four minutes into the second period.
Routledge provided the opening, and Rangel volleyed home with his right foot in off the far post.
Latics could have few complaints such was the sluggish way they re-emerged from the dressing room.
But they were quickly back into their strike and McCarthy restored the lead within three minutes.
The Ireland international drove his way through the midfield off a fine pass from Caldwell, and his finish was low and true and flew past Vorm into the bottom corner.
Latics had a great opportunity to make it 3-1 moments later when Kone cross’s saw McArthur scuff his shot wide from close range.
And the fragile nature of a one-goal lead was shown again on the hour mark when a mistake from Caldwell allowed Shechter in to score with his left foot.
The end-to-end nature of the game continued into the final half-hour, with Latics needing all three points and mid-table Swansea having no reason to settle for a point.
There was a big shout for handball when Espinoza’s cross appeared to hit the arm of Rangel, while Latics came agonisingly close to taking the lead for a third time at the three-quarter mark.
Maloney’s corner was headed powerfully goalwards by Caldwell, only for Vorm to tip the ball over the top with his fingertips.
The resulting corner found Franco di Santo - on for McManaman - but this time the ball looped harmlessly wide for a goal-kick.
Nathan Dyer came on for Swansea with 21 minutes left, and the Welsh side took a dramatic lead with 14 minutes remaining.
It was another poor goal for Latics to concede, the defence failing to clear the ball on countless occasions and keeping the visitors interested.
A mistake by Espinoza saw Pablo Hernandez lob the ball to the far post.
There was more confusion between Maloney and McArthur, and Tiendalli responded by scuffing the ball past Joel and past the desparing challenge of Caldwell.
Latics had given themselves a mountain to climb, and they had to wait an eternity for the chance to respond after a sickening collision between Davies and Vorm saw the goalkeeper stretchered off.
Martinez used the break to get Gomez and Stam on for Watson and Emmerson Boyce, but the Dutchman’s first involvement saw him pick up an injury to his left shin.
Gomez was quickly into the game to tee up Kone, although his shot was wide of the far post.
Wigan’s cause wasn’t helped when Stam was unable to return to the field, the right-back retaking his place on the bench to leave his side to play the nine minutes of added time with 10 men.
They tried hard but couldn’t make it count, and only a fine save from Joel right at the death prevented Dyer a fourth goal on the break.
Latics: Joel; Caldwell, Watson, Scharner; Boyce, McCarthy, McArthur, Espinoza; Maloney, McManaman, Kone.
Subs: Al Habsi, Stam (for Boyce, 85), Golobart, Jones, Gomez (for Watson, 85), Di Santo (for McManaman, 64), Henriquez.
Swansea: Vorm; Rangel, Williams, Monk, Davies; Tiendalli, Britton, De Guzman, Routledge, Hernandez; Shecter.
Subs:Tremmel (for Vorm, 85), Bartley, Naylor, Dyer (for Shecter, 69), Moore, Agustien (for Hernandez, 76), Donnelly.
Referee: Kevin Friend