The boot of France scrumhalf Maxime Machenaud guided Racing 92 to a 26-20 victory over Clermont in Sunday's clash of the Top 14 heavyweights.
Machenaud kicked seven penalties to go with Albert Vulivuli's try as the Parisian's inflicted a first defeat in nine fixtures on the league leaders.
Clermont outscored their hosts two-to-one on the try-count, with Aurelien Rougerie and Damien Chouly touching down for one each in the first half. However, after managing just two penalties in the second period, Clermont were left to rue the accuracy of Machenaud from the tee.
In Saturday's action, Toulouse gave their play-off hopes a shot in the arm with a 12-10 victory over a disjointed Toulon.
All of Toulouse's points came from the boots of Sebastien Bezy and Florian Fritz, who scored a brace of penalties each at the Allianz Riviera in Nice.
Toulon were limited to a solitary penalty from Eric Escande, until Juan Smith touched down for the game's only try after 79 minutes. Jonathan Pelissie duly converted but, with just seconds remaining, there was not enough time for Toulon to convert their superior possession into victory.
The win leaves Toulouse in fifth place on 61 points, three ahead of Castres in sixth and four ahead of Bordeaux in seventh. Only the top six teams qualify for the play-offs.
Castres kept up the pressure on Toulouse with a 37-6 thrashing of Pau, touching down for six tries as they cruised to victory.
Those tries came from Geoffrey Palis, Ben Urdapilleta, Karena Wihongi, David Smith, and a Marc-Antoine Rallier brace. The scoreline could have been even worse for Pau had Urdapilleta found his kicking boots. The Castres fly-half missed four conversions at Stade Pierre-Antoine.
Stade Francais' woes continue after they suffered a 35-25 defeat by Bordeaux, whose victory ensured they are still breathing down the necks of Castres in the play-off spot above them.
Adam Ashley-Cooper opened the scoring for Bordeaux with a ninth-minute try, with the Australian's touchdown followed by scores from Clement Maynadier, Metuisela Talebula Maijaina, and a penalty try. Stade's three scores -- all in the second-half -- came from Jeremy Sinzelle, Waisea Nayacalevu Vuidravuwalu, Meyer Bosman.
Elsewhere, Montpellier ran in seven tries in a 51-10 demolition of Grenoble, bottom-placed Agen produced a shock 37-19 over mid-table Brive, and Oyonnax edged past La Rochelle 17-16.