Judicael Cancoriet is set to have surgery on a torn pectoral tendon but could still return for the Top 14 playoffs.
Ryan Mills' last-gasp drop goal put Worcester Warriors into the last eight of the Challenge Cup for the first time in a decade.
Clermont Auvergne hammered fellow title hopefuls La Rochelle, who had won 10 of their previous 11 matches.
The battle between top and bottom in the Top 14 table stayed true to form, Clermont running out comfortable winners on the road.
The top two in the Top 14 table could not be separated as Clermont Auvergne and Toulouse shared a thrilling draw.
Isaia Toeava will undergo surgery on a ruptured rotator cuff in his left shoulder, ruling him out for six months.
La Rochelle's perfect record in the Challenge Cup was ended by Bristol, but Clermont Auvergne claimed a fourth win out of four.
There were wins for the Ospreys, Sale Sharks and Clermont Auvergne in the European Challenge Cup on Saturday.
Montpellier's late rally did not deny Top 14 leaders Clermont Auvergne a 28-23 victory, while Guilhem Guirado scored a try in Toulon's win.
There were wins for Clermont Auvergne and La Rochelle in the Top 14 on Sunday.
Clermont Auvergne could only draw with lowly Grenoble and Toulouse took advantage by putting Bordeaux-Begles to the sword in the Top 14.
Clermont still lead the way in Top 14, but Stade Francais remain on their heels after a late win over Montpellier.
Connacht had no answer to Chris Ashton, who enjoyed a hat-trick on his competitive debut for Sale Sharks.
Worcester Warriors had lost 11 away games in a row in the Challenge Cup, but ended that sequence with a brilliant showing in Paris.
Clermont's advantage at the summit of the Top 14 table was reduced to four points after they were beaten at La Rochelle.
Top 14 leaders Clermont Auvergne put some daylight between themselves and second-place Stade Francais on Saturday.