Three-time French champions Castres will look to build on their stunning start to the Top 14 campaign on Friday with an eighth successive win when they host Racing-Metro.
Castres, who have not won the title since 1993, are building on the good impression they made last season when they reached the play-offs only to be beaten by eventual finalists Montpellier.
They face a Racing-Metro side that has struggled to make an impact this season, failing unlike Clermont who top the table with Castres, to cope without their players who were away at the World Cup.
The expensively-assembled Paris-based outfit have won just three of their eight matches and went down to Toulon at home last Saturday which sees them in seventh spot, 13 points adrift of the two leaders.
Castres have virtually no injury problems and their only selection poser is whether to recall their record points scorer fullback Romain Teulet or leave the in-form outfit intact.
Castres have certainly not missed Teulet's kicking ability as South African Rory Kockott showed last Saturday when he landed seven penalties in the 21-16 victory over Montpellier.
Despite Racing desperately needing a win to re-energise their campaign sporting director Pierre Berbizier is likely to rest star Argentinian Juan Martin Hernandez, who only returned after a seven month injury absence in the 16-9 defeat by Toulon.
Berbizier doesn't want to give the 'Magic man' a second tough match in such a short space of time, on the other hand he is set to start another Argentinian Juan Jose Imhoff, who has been signed as emergency injury cover for the injured French wing Benjamin Fall.
Racing know, though, that they are facing a tough challenge in travelling to Castres.
"It is a complicated match," admitted centre Guillaume Bousses.
"Castres are the star side of the beginning of the season.
"We are also without quite a few players. We will go there with all our minds set on doing our best, but it will be difficult. We are not defeatist but we know what awaits us: a really tough match."
Should Castres win they should be rejoined at the top on Saturday as Clermont host Biarritz, with the latter side surprisingly the tailenders with just one win this season and desperate for their French stars to return to club action after their epic World Cup campaign.
This week's fixtures:
Friday, October 28
(Kick-off 18.45 GMT)
Castres v Racing-Metro
Saturday, October 28
(Kick-offs 12.15 GMT unless stated)
Bayonne v Perpignan
Bordeaux-Begles v Lyon
Toulon v Brive
Clermont v Biarritz
Toulouse v Stade Francais (14.15)
Agen v Montpellier (18.45)
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