Ander Herrera of Manchester United scores the opening goal during the Barclays Premier League match between Swansea City and Manchester United at Liberty Stadium on February 21, 2015 © Getty Images

United had their backs to the wall early on when Gylfi Sigurdsson picked out Gomis, who saw his header beat David de Gea before it was cleared off the line by Herrera.

Louis van Gaal's men were under the cosh from the kickoff and Gomis returned again to threaten the United defence from a corner, only for his second headed effort to fly over the bar without troubling De Gea.

Despite the early pressure, United almost took the lead in the 15th minute through Robin van Persie, but he flashed an effort across the face of goal after Angel Di Maria's set piece.

Lukasz Fabianski had to be alert five minutes later as Wayne Rooney found just enough space to get a shot off towards the bottom corner, which was obligingly kept out by the Polish stopper.

Some United fans have called for Herrera to feature more in the Premier League and he stated his case for more starts with a fine strike across the face of goal to put the visitors ahead in the 28th minute.

Their lead was to last just two minutes, however, as Jonjo Shelvey turned in a delivery to the near post, where Ki broke past some poor defending to tuck into the bottom-right corner.

Swansea player Ki Sung-Yueng scores the first Swansea goal during the Barclays Premier League match between Swansea City and Manchester United at Liberty Stadium on February 21, 2015 © Getty Images

Ki apeared menacing in the early stages of the second half and he drew a world-class save from De Gea after profiting from another smart ball from Shelvey.

The quiet Van Persie sought to benefit from Rooney's through ball, only to guide his shot wide of the left post, while Marcos Rojo also headed horribly wide at the back stick from a Di Maria corner.

Despite United's second-half dominance, Swansea pushed ahead thanks to Gomis, who deflected a long-range shot from Shelvey past a helpless De Gea to make it 2-1.

Wayne Routledge did his best to try to kill the game off with five minutes to play when he broke away to find Gomis, who saw his shot saved by De Gea in the centre of the United goal, but the Swans had already done enough.