Leaders Ulster fell to only their second RaboDirect PRO12 League defeat of the season when their weakened side was outplayed 16-12 by an Ospreys outfit that, despite missing even more squad members than their hosts, outplayed the Ravenhill squad.
In a closely-contested game that was nip and tuck until the later stages, it took a breakaway try by Ospreys prop Ryan Bevington to seal the four points for the visitors who at that stage were reduced to 14 men after Morgan Allen had been sin-binned moments earlier. Matthew Morgan converted Bevington's try and added three penalties for the away side.
Ulster had to be content with the losing bonus point from their first home league defeat since succumbing to Leinster in April 2012 and they may also have to do without star player Ruan Pienaar, who kicked over three penalties before he was taken off in the second half with a shoulder injury. Stuart Olding added Ulster's final penalty.
While Newport Gwent Dragons came from behind to score 17 unanswered points and secure a desperately-needed 23-14 victory over Italian outfit Benetton Treviso at Rodney Parade.
Treviso looked to be in the driving seat after they led 14-6 at the break courtesy of tries from centre Doppies La Grange and replacement back row Filippo Giusti.
But the Dragons, whose only points in the first period came from the boots of Steffan Jones and wing Tom Prydie, turned the match on its head as both men added tries and Prydie kicked seven extras.