Castres Olympique full-back Julien Dumora was on top form as his side ran riot against Scarlets to win 34-16.
Castres Olympique were the main force of the first half, with Scarlets suffering two sin bins. The first came almost as soon as the match started, wing Steff Evans at fault, with the second coming in the 31st minute with scrum-half Kieran Hardy punished.
It meant Castres were able to rack up four tries via wing Josaia Raisuqe, fly-half Louis le Brun, scrum-half Jeremy Fernandez and Number 8 Abraham Papalii, with Le Brun only able to convert one.
All of Scarlets points came from the boot of Ioan Lloyd, who did his best to keep his side in it with three penalties.
The second period didn’t start well for the Welsh region either, with Dumora going over for a converted score.
There was some hope when Lloyd struck to score Scarlets’ first try, which he converted himself, but Castres reinforced their lead when Le Brun kicked a penalty.
The fly-half then added even more to the scoreboard with his second converted try, finishing off a wonderful series of offloads with a well-timed, arching run.
However in the closing stages, both he and Antoine Bouzerand saw yellow as the match ended on a sour note.