The top two in the Top 14 claimed huge victories to stay unbeaten as both the defending champions and last year's runners-up were beaten.
The second round of Top 14 fixtures saw hard-fought wins for Clermont Auvergne, La Rochelle and Montpellier, among others, on Saturday.
There were shock wins for Bayonne and Bordeaux-Begles as the Top 14 returned for the 2019-20 season on Saturday.
There will be a new Top 14 champion after Castres missed out on a top-six finish with a final-day defeat to Toulon.
Neither Bordeaux Begles nor Stade Francais can make the play-offs in the Top 14 after suffering painful defeats in the penultimate round.
Former South Africa head coach Heyneke Meyer will remain with Stade Francais for at least another two years.
It promises to be an enthralling climax to the battle for Top 14 play-off spots after Stade Francais claimed a derby win over Racing 92.
Greig Laidlaw's boot and a pair of tries from Apisai Naqalevu helped Clermont Auvergne battle back to beat Stade Francais on the road.
La Rochelle put Pau to the sword and Castres also enhanced their chances of reaching the play-offs with a win in Bordeaux.
Toulon may have been at a numerical disadvantage for most of the second half but they still managed to defeat Top 14 leaders Toulouse.