Bordeaux fly-half Sanchez scored an early try before Robert Lilomaieva and Jefferson Poirot crossed in the final 12 minutes. But it was three yellow cards for Dragons forwards that proved just as decisive as the visitors’ discipline deserted them at Stade Andre Moga.

Toby Faletau crossed before half-time to hand the Dragons a chance of a rare victory on French soil but it was not enough to compensate for an error-strewn display.

Dragons could have overtaken Bath at the top of the pool if they had repeated last week’s 40-22 win over the same opposition but Bordeaux proved too strong on home soil. The result leaves Bath three points clear ahead of their game against Rugby Mogliano and in the driving seat for a place in the last eight.

Jason Tovey handed Dragons an ideal start with a penalty as early as the second minute but they failed to build. Instead, opposite number Sanchez took charge, kicking the equaliser before skipping through for the game’s opening try, which he converted, after just seven minutes.

Dragons struggled to match the sheer brute force of the Bordeaux scrum and a string of penalties saw them trail 19-6 when skipper Andrew Coombs was shown a yellow card for dangerous play, when he tackled an opponent in mid-air.

Yet when his team were most in need of a lift, it came in the familiar shape of Faletau who bustled over five minutes before half-time and Tovey’s conversion handed Dragons a lifeline at 19-13.

But Lewis Evans’ discipline slipped just two minutes into the second half and he handed Sanchez a further three points when he was binned. Briefly reduced to 13 men, Lyn Jones’ side showed remarkable resilience to hold out a giant Bordeaux pack but no sooner were the captain and back-row back on the field than Robert Sidoli was shown a yellow card and Lilomaieva raced over.

Mistakes mounted for the young Dragons and defensive lapses saw Poirot clinch what appeared an inevitable third try for Bordeaux and left the visitors empty-handed.