Barnsley lost 1-0 at home to high-flying Cardiff City who scored an 83rd-minute winner in a dull match on Tuesday.
Barnsley had marginally the better of the pressure and chances but lacked the quality to break down the Championship's best defence before Callum Paterson got the winner.
The result ended Barnsley's run of four games unbeaten and left them 17th In the table with 20 points from 17 games.
Paul Heckingbottom made five changes to the side that drew at Norwich City on Saturday. Top-scorer Tom Bradshaw and star winger Harvey Barnes dropped out of the 11, as did George Moncur, the suspended Joe Williams and injured captain Angus MacDonald. Coming into the side were Matty Pearson, Cameron McGeehan, Gary Gardner, Ryan Hedges and Mamadou Thiam who played on his own up front in a 4-5-1 formation.
The first quarter of the match was very dull, with a long range shot from Joe Bennett which was straight at Adam Davies, being the only moment of action.
Thiam had a quiet start but began to impose himself on the game, testing visiting goalkeeper Neil Etheridge with a low 25-yard effort on 28 minutes. The French striker then had the best chance of the first half but headed wide when unmarked from close range after meeting a good Brad Potts cross following a clever back heel by Hedges.
Adam Hammill and Liam Lindsay were both off target with long-range efforts then Potts made a mess of a good headed opportunity. Barnsley went into the break having been marginally the better side in a dull 45 minutes.
Two minutes into the second half, Potts had a shot from 30 yards which was straight at Etheridge then Craig Bryson shot wide from 20 yards out at the other end before Junior Hoilett cut in from the left but his shot from 12 yards was straight at Davies.
Heckingbottom introduced Barnes, Bradshaw and Moncur for Hedges, Thiam and McGeehan, who had just sent a 25-yard free-kick over the bar. Hammill had another long-range effort but again the shot whistled well wide.
The winning goal came on 83 minutes when Sol Bamba's header from a corner was cleared off the line by Hammill but Liam Lindsay's attempted clearance hit Callum Paterson and the ball flew in.
Barnsley almost levelled instantly but Pearson was inches away from connecting with a Hammill free-kick.
