The Ospreys were left counting their first-half errors as Perpignan claimed a hard-fought 17-15 victory at Stade Aime-Giral on Saturday.
With the moonlighting Dan Carter sidelined due to an Achilles injury, the Catalans were minus their star signing but boosted up front by returning Henry Tuilagi's imposing frame at the base.
And in fact the loss of Carter proved that one man does not make a team as the New Zealander's replacement, Steve Meyer, stood out with a heads-up style that was made possible by his number eight's constant graft.
The hard-running Samoan, who was playing in his competition debut this season, did take a good 40 minutes to regain his European match pace, but from that point on he became the architect of Perpignan's success with a typical close-range try before the Ospreys finally clicked into gear.
However, in front of a partisan crowd, the international-filled visitors did prove why many have dubbed them serious contenders for the coveted silverware as the sheer class of Shane Williams and Tommy Bowe came to the fore in claiming a vital losing bonus point.
It was a contest that remained deadlocked fifteen minutes into the game as the impressive away runners' attempted probes on the outside shoulder found little charity from their physical hosts.
And when that early storm was weathered, a long-range Meyer penalty goal seemingly turned the tide with another three points soon doubling their lead to bring the colourful crowd to their feet.
Frustration subsequently began to creep into the Ospreys game as precision of passes dropped for a period with promising attacking platforms blown.
Sean Holley's side knew that fellow Pool rivals Leicester were extremely likely of claiming five points at home to Treviso - which would set up a Liberty Stadium finish against the English - so a losing bonus point would not be too shabby in the situation.
However, their predicament was made tougher when the scoreline was stretched to 12-0 thanks to Mike Phillips killing the ball with matters looking worrying. An improvement was needed on the turnaround.
That did not come though as Perpignan continued to apply the squeeze with the returning Phillips charged down by impressive youngster Damien Chouly, ultimately earning his side a touch-finding penalty - a signal of intent with three points on offer.
And it proved the right decision as Tuilagi's growth into the contest came to the fore with a typically bulldozing finish from close-range to push the Catalans further ahead.
That looked to have ended the Ospreys' limp effort until they showed why they are one of the best counter-attacking teams in Europe by sparking to life on the hour.
First the wily Phillips began the breakout move from his own half before handing on to the supporting Alun-Wyn Jones, who shifted it to wing Williams who announced his side on the board.
Was it to be a remarkable comeback? The international-filled side certainly sensed that could be a possibility as opportunities continued to come while in good territory. Lock Jones became increasingly involved in proceedings as he joined Phillips and the usual late-game roams from Williams.
And the grandstand finish was created on 68 minutes as sustained pressure and a succession of phases finally told on the French tacklers. Irish wing Tommy Bowe was the architect this time as he attacked the shoulder of a front-row before casually offloading to substitute Jonny Vaughton to cross.
Moving into the final ten minutes and the tag of becoming the first Welsh team to leave Perpignan victorious was dangling ever closer after a Hook penalty four minutes from time reduced the lead to just two points, but the Ospreys left it all too late.
Pen: Meyer 4
Tries: Williams, Vaughton
Perpignan: 15 Philip Burger, 14 Christophe Manas, 13 David Marty, 12 Maxime Mermoz, 11 Julien Candelon, 10 Steve Meyer, 9 Chris Cusiter, 8 Henry Tuilagi, 7 Damien Chouly, 6 GrÃ©gory Le Corvec, 5 Olivier Olibeau, 4 Rimas Alvarez Kairelis, 3 Nicolas Mas, 2 Guilhem Guirado, 1 Kisi Pulu,
Replacements: 16 Charles Geli, 17 Sebastien Chobet, 18 Guillaume Vilaceca, 19 Jean-Pierre Perez, 20 Gavin Hume, 21 Nicolas Durand, 22 JÃ©rÃ´me Porical.
Ospreys: 15 Lee Byrne, 14 Tommy Bowe, 13 Andrew Bishop, 12 Gavin Henson, 11 Shane Williams, 10 James Hook, 9 Mike Phillips, 8 Filo Tiatia, 7 Marty Holah, 6 Ryan Jones (c), 5 Alun-wyn Jones, 4 Ian Gough, 3 Adam Jones, 2 Richard Hibbard, 1 Paul James.
Replacements: 16 Huw Bennett, 17 Cai Griffiths, 18 Lyndon Bateman, 19 Tom Smith, 20 Jamie Nutbrown, 21 Dan Biggar, 22 Jonny Vaughton.
Referee: Alain Rolland (Ireland)
Touch judges: David Keane (Ireland), Brian MacNeice (Ireland)
Television match official: John Sheehan (Ireland)
Assessor: Steve Lander (England)