Dragons hopes of qualifying for the knockout stages of the European Challenge Cup hang in the balance after a 42-14 defeat to French heavyweights Castres Olympique at Stade Pierre Fabre.
Dragons had previously won three times on French soil, but they always faced a stern test against a Castres side who had not lost at home in Europe since 2015.
The former Top14 champions wrapped up the bonus point just after half-time after a brutal display of power and pace in the south of France.
Dragons struck blows with a superb double try burst from impressive wing Jared Rosser.
But all eyes now turn to the home game with Enisei-STM next Friday evening at Rodney Parade when Dean Ryan’s men know only a convincing win will be enough.
The hosts, buoyed by a boisterous home crowd, flew out of the traps with a devasting double early blow.
Elusive home fly half Thomas Fortunel jinked his way over for the opening try, converted by Julien Dumora, before a stunning second that had the home fans on their feet.
Wing Filipi Nakosi rolled out of a tackle down the right flank and cleverly chipped ahead for the marauding back row Anthony Jelonch to collect and dive over. Dumora added the extras for a 14-0 lead after 11 minutes.
Dragons, forced into a late change with Jack Dixon called into the starting line-up for Adam Warren, were looking to run the ball whenever possible.
Wing duo Rio Dyer and Jared Rosser were hungry for work and Ross Moriarty charged down one clearing kick to spark home alarm.
Castres, though, looked very menacing up front and grabbed a third try as tighthead prop Wilfrid Hounkpatin bulldozed over from close range after a five-metre scrum.
Dragons almost hit back immediately as Tom Griffiths broke the home defensive line, but his inside pass found a tumbling Knoyle who fell to the turf yards from the line as he gathered the pass.
Another break down the left wing was worked inside for the direct Taine Basham to hurtle up close before Rosser was bundled into touch just short after he raced down the right.
Huge pressure before the break saw Dragons thump away at the home try line to no avail as Castres took a commanding 21-0 lead to the dressing room.
The home side extended the lead in ominous fashion as they started the second half as fast as the first with two quick-fire scores.
Full back Dumora launched an attack from deep that went through the hands to big man Nakosi before Thomas Combezou arched his run and grabbed the try bonus point.
And then Dumora glided over himself in the corner to reward his man-of-the-match display, after another powerful home drive had sucked in defenders.
Dragons continued to valiantly look for a way into the game but were finding a brutal Castres defence in no mood to take their foot off the gas in the final quarter.
However, a moment of superb skill from Rosser saw him breakthrough as he gathered a loose ball, kicked ahead and raced past two men before beating the covering full back to touch down for a fine individual score.
Castres responded with more brute power up front as a driving maul crashed over with replacement hooker Kevin Firmin touching down.
But it was Rosser, and the battling Dragons, who were to have had the final word as the wing broke out of one tackle and held off another to stretch over the line for his personal double.
07m Fortunel t Dumora c 7-0
11m Jelonch t Dumora c 14-0
24m Hounkpatin t Dumora c 21-0
45m Combezou t Dumora c 28-0
52m Dumora t Dumora c 35-0
65m Rosser t S. Davies c 35-7
72m Firmin t Dumora c 42-7
79m Rosser t S. Davies c 42-14
Castres: Julien Dumora, Filipo Nakosi (Laveau 49), Thomas Combezou (Vialelle 63), Yann David, Taylor Paris, Thomas Fortunel, Rory Kockott (Radosavljevic56); Matthew Tierney (De Benedittis 66), Jody Jenneker (Firmin 52), Wilfird Hounkpatin (Wihongi 52), Loic Jacquet, Victor Moreaux (Samson 8), Baptiste Delaporte, Anthony Jelonch, Alex Tulou
Replacements: Kevin Firmin, Wayan de Benedittis, Karena Wihongi, Christophe Samson, Camille Gerondeau, Ludovic Radosavljevic, Florian Vialelle, Martin Laveau
Dragons: Jacob Botica (Penny 66), Jared Rosser, Tom Griffiths, Jack Dixon, Rio Dyer, Sam Davies, Tavis Knoyle (R. Williams 53); Lloyd Fairbrother (Reynolds 66), Elliot Dee, Leon Brown, Joe Davies (Keddie 59), Matthew Screech, Cory Hill (c), Taine Basham, Ross Moriarty
Replacements: Ellis Shipp, Josh Reynolds, Chris Coleman, Max Williams, Harrison Keddie, Rhodri Williams, Jack Dixon, Carwyn Penny
Referee: JP Doyle (Eng)