Castres turned on the style in the second half of their Top 14 clash with Bordeaux Begles on Sunday to win 29-17 and boost their hopes of a top-six finish.
A tight but entertaining opening 40 minutes saw visitors Castres go in 16-14 ahead, tries from Horacio Agulla and Anthony Jelonch making the difference.
Bordeaux's chances of a turnaround dwindled after the break and even a yellow card for Mathieu Babillot failed to halt Castres' momentum.
Two penalties from Julien Dumora and a converted Marc-Antoine Rallier try extended Castres' advantage, while stretching Bordeaux's winless run to six league games.
Castres briefly occupied third place in the table, but Montpellier finished the day in that spot after a 27-18 win over Toulouse.
A Paul Willemse try was converted by Willie du Plessis to cancel out Sebastien Bezy's early penalty and Du Plessis added another two kicks as Montpellier opened up a 10-point advantage just before the break.
Toulouse did edge the second-half scoring 15-14 as Census Johnston and Alexis Palisson crossed, but it was not enough, with Timoci Nagusa and Yvan Reilhac responding for the hosts.