Wanderers' recent upturn in form came to an abrupt halt against Fulham.
Three straight wins had seen the club lift themselves out of the bottom three – but they seldom looked anything like the side of recent weeks.
Clint Dempsey struck twice for the West Londoners to take his tally for the season to 21, before Senegalese midfielder Mahamadou Diarra added his first goal for the club in the closing stages.
It was a limp and lifeless performance from the Whites, who succumbed in similarly disappointing fashion to Fulham at Craven Cottage back in December.
The visitors took their chances in what was a fairly turgid first half, with Damien Duff enjoying the freedom of the right wing against an ineffectual Marcos Alonso.
Dempsey opened the scoring with a free-kick from the very top drawer.
David Ngog had needlessly hauled Mahamadou Diarra down 25 yards out, and the in-form midfielder unleashed a sweetly struck right-footed effort into the top corner to give Adam Bogdan no chance.
Duff continued his torment of Alonso on the wing. And after the experienced Irishman had cut inside his marker and fizzed one shot just wide of the post, he then went on the outside moments later to chip a cross for the unmarked Dempsey to head home from six yards.
The American's 15th goal of the season made him the most prolific Fulham player in a single Premier League season and brought about a chorus of boos at the half time interval from the home fans.
Owen Coyle threw on Kevin Davies and Chris Eagles after the restart for Ryo Miyaichi and Darren Pratley and the early signs were that Wanderers could haul themselves back into the game.
Martin Petrov latched on to a knock down from Davies to volley just wide and Eagles went close with a free kick.
Ngog wasted a brilliant chance of his own making when, after nicking the ball round Aaron Hughes, he then had his pocket picked by John Arne Riise as he wound up to shoot for goal.
Any momentum quickly drifted away, however, and but for Bogdan it could have been a landslide victory for the Cottagers.
Duff twice got behind Alonso to force the Hungarian stopper into action but there was nothing he could do eight minutes from full time when Riise surged down the left, and crossed low for Diarra to smash home from close range.
The defeat leaves Wanderers a place and a point above the relegation zone heading into Easter Monday's game against in-form Newcastle United.