Hooker Guilhem Guirado made a nightmare start to his Montpellier career, suffering a long-term injury on his debut against his former club.
Wing Teddy Thomas put more pressure on Stade Francais coach Heyneke Meyer as Racing 92 came out on top in the Paris derby.
Toulouse's contrasting home and away form continued as they defeated visitors and 2018-19 Top 14 final opponents Clermont Auvergne.
Jake McIntyre was accurate off the tee as Clermont Auvergne stopped Lyon in their tracks in Sunday's Top 14 encounter.
An early red card was decisive as Bordeaux-Begles suffered their second defeat of the Top 14 season.
Agen hooker Paula Ngauamo is set to miss seven weeks for his Top 14 club following an incident during the Rugby World Cup.
Kylan Hamdaoui scored late as Top 14 strugglers Stade Francais edged out Toulon, while Bordeaux-Begles ran riot against Clermont Auvergne.
It was another game and another win for Lyon in Top 14, where Castres were defeated by Toulouse on Saturday.
Racing 92 dominated the second half to beat Pau before La Rochelle were beaten by Toulon at Stade Mayol.
Leaders Lyon are the only unbeaten side in the Top 14 after they won a top-of-the-table encounter against Bordeaux-Begles.