Clermont Auvergne endured further home misery on Saturday, suffering a 19-15 defeat to Montpellier on their return to Top 14 action.
Last season's European Champions Cup runners-up made a humiliating exit from that competition last weekend, when Morgan Parra's decision to take a quick tap in front of the posts against Bordeaux-Begles prevented Clermont from kicking an 80th-minute penalty that would have secured top spot in Pool Two.
And there was to be no shot in the arm for Clermont this weekend as they lost ground at the top of France's domestic top flight.
Marvin O'Connor scored the only try of the match as Montpellier opened up a 16-3 interval lead, before holding off a Clermont fightback that at least secured a losing bonus point.
Racing 92 and Toulouse each capitalised on Clermont's slip-up to pull four points clear of the latter.
Tries from Henry Chavancy, Juan Imhoff, Dan Carter and Yannick Nyanga helped Racing to a 26-3 victory over lowly Oyonnax at Stade Yves-du-Manoir.
Toulouse recorded an even more comprehensive triumph, Sebastien Bezy and Maxime Medard each crossing twice in a 54-3 thrashing of Pau.
Johnnie Beattie's late score sealed a 19-9 win for Castres at home to Bordeaux, who slipped below their opponents in the table as a result.
Rock-bottom Agen were beaten 33-27 by Grenoble in a thrilling match at Armandie Stadium featuring five tries, nine penalty goals and the dismissals of Remy Vaquin and Sona Taumalolo following a first-half brawl.