Cardiff Blues were knocked off the top of Pool Two by Perpignan in a hugely damaging Heineken Cup defeat at home.
HEINEKEN CUP POOL TWO
Blues: (3) 3:
Perpignan: (5) 21:
Tries: Grandclaude, Marty.
Pens: Laharrague 3.
The Catalan-based French side are now favourites to qualify automatically for the quarter-finals after a powerful performance that strangled the Blues.
The home side were limited to just a solitary Nick Macleod penalty.
Jean-Phillipe Grandclaude's try gave Perpignan a 5-3 lead, while after the break David Marty also crossed and Nicolas Laharrague kicked 11 points.
With Perpignan having a home match against group minnows Calvisano next week, the Blues - who go to Leeds - are now realistically looking at second place at best.
The Cardiff side must pull out all the stops for a handsome win over the Tykes and then keep their fingers crossed in the lottery for one of the two best runners-up spots that lead to the knock-out stages.
Macleod kicked his penalty after five minutes to give the Blues an early lead, while opposing fly-half Laharrague was wide with his only chance in the first quarter.
But Perpignan struck back with an unconverted try as the Blues fluffed their defensive lines.
First Martyn Williams was brushed aside by Perpignan hooker Marius Tincu, who galloped up the middle before shipping the ball to left wing Grandclaude.
Blues skipper Rhys Williams perplexingly refused to come forward to make the tackle, giving Grandclaude room to muscle in at the corner as Williams at last - far too late - tried to stop his man.
Laharrague's first successful kick of the afternoon, a simple penalty seven minutes after half-time, was soon followed by his second and then a third.
In a game that had been so delicately poised, the 14-3 lead that the Catalans had now opened up looked more than handy.
The Blues were enjoying their fair share of possession, but the Cardiff side found themselves being shunted backwards in the tackle as Perpignan sensed the match was there for the taking.
MacLeod, only playing because of injury to Nicky Robinson, fell short with a 40-meter penalty from in front of the posts and was soon replaced by Roger Warren at fly-half.
If that change was tactical by Blues coach Dai Young, the departure of Rhys Thomas - Duane Goodfield taking over - was injury enforced.
The Wales hooker went off clutching a damaged wrist and, with the Six Nations looming, national coach Mike Ruddock will have his fingers crossed that the injury is not as bad as it first appeared.
Perpignan then struck the killer blow that put the result beyond doubt and probably booked their place in the quarter-finals.
Laharrague's clever chip over was overran by Rhys Williams and replacement centre Marty was on hand to touch down, Laharrague rounding things off with the conversion.
Cardiff Blues coach Dai Young:
"We have got to be honest and realistic and for most parts of that game we weren't really in it.
"I thought we were outplayed. We played a lot of rugby around the halfway line, but we didn't really go anywhere.
"We know what we have got to do in the last game against Leeds and we have got to pull ourselves together."
Perpignan full-back Manny Edmonds:
We pinpointed Jonah Lomu's weaknesses going backwards and we targeted him, but I do think Cardiff can use him better than they did."
Blues: Rhys Williams (capt); Craig Morgan, Jamie Robinson, Marc Stcherbina, Jonah Lomu; Nick Macleod, Mike Phillips; Gethin Jenkins, Rhys Thomas, Martin Jones; Deiniol Jones, Robert Sidoli; Andy Powell, Martyn Williams, Xavier Rush.
Replacements: Roger Warren for MacLeod (61), John Yapp for Jenkins (63), Duane Goodfield for Thomas (65), Craig Quinnell for D Jones (66), Robin Sowden-Taylor for Powell (77). Not Used: Ryan Powell, Lee Thomas.
Perpignan: Manny Edmonds; Christophe Manas, Gavin Hume, Jean-Phillipe Grandclaude, Samueli Dawai-Naulu; Nicolas Laharrague, Nicolas Durand; Perry Freshwater, Marius Tincu, Nicolas Mas; Colin Gaston, Nathan Hines; Gregory Le Corvec, Bernard Goutta (capt), Scott Robertson.
Replacements: David Marty for Grandclaude (40), Vincent Debaty for Freshwater (78), Michel Konieck for Tincu (68), Viliani Vaki for Le Corvec (68), Rimas Alvarez Kairelis for Goutta (78), Ovidiu Tonita for Robertson (78). Not Used: Sylvain Dupuy.
Referee: Tony Spreadbury (England)