Springbok Kolbe carted off in Toulon win with ankle injury
Kolbe, who played five games of the Springboks' Rugby World Cup campaign in 2019, left the field in the 36th minute after scoring a try at Stade de Gerland.
Broadcaster Canal+ said the 29-year-old had suffered a sprained ankle as he bounced off the ground after diving to touch down.
The winger, who made the last of his 24 Test appearances in November, was in tears as a golf buggy carried him to the stands, a worrying image with this year's World Cup in France less than six months away.
Samoa centre Duncan Paia'aua and Fiji's Waisea Nayacalevu also crossed for the visitors, who moved into the top six play-off spots as the Top 14 returned after a two-week break following the end of the Six Nations.
Elsewhere, Italy fly-half Paolo Garbisi kicked a 77th-minute penalty as champions Montpellier edged lowly Perpignan 23-22.
Bayonne lost at home for the first time since January 2022 as Georgia prop Guram Papidze crashed over in Pau's 30-20 win.
The game was played in front of a sold-out 40,000 Reale Arena in San Sebastian as the Basques returned to the ground for the first time since 2014.
Bottom of the table Brive finished the 38-10 defeat at Clermont with 13 men after Fijian centre Setareki Bituniyata and South Africa prop Marcel van der Merwe were shown red cards in the final 10 minutes in front of a packed Stade Marcel-Michelin.
Argentina fly-half Benjamin Urdapilleta slotted 14 points as Castres beat leaders Toulouse 27-17 to take a step closer to maintaining their place in the top flight.
The hosts moved seven points clear of the relegation play-off place with just their third win since December also thanks to full-back and skipper Julien Dumora's double.
After next weekend's break for the Champions and Challenge Cups, Castres face Montpellier, Toulon, Pau, Brive and Perpignan in the run-in.
"It's another step that we've taken today," Dumora said. "There are five more remaining to keep the club up."
Second-placed La Rochelle defeated Bordeaux-Begles 36-6 in front of another full house -- 42,000 at the city's football ground, the Matmut Atlantique.
La Rochelle made the most of an indisciplined Bordeaux side who conceded 16 penalties as they remain six points behind Toulouse.
On Sunday, third-placed Stade Francais welcome Racing 92 in the Parisian derby.