Toulouse climbed to the summit of the early Top 14 table with a 28-8 home victory over Toulon on Sunday, but saw France fly-half Romain Ntamack limp off with an ankle injury.
The hosts scored four tries for a bonus-point success which took them above European champions La Rochelle, the only other side to have won their first two matches.
But Ntamack sprained his ankle and back-row Francois Cros hobbled off just minutes after coming on with a recurrence of a knee injury he suffered at the end of last season.
Toulouse backs coach Clement Poitrenaud said Ntamack's inital medical test was "reassuring".
Ntamack missed out on the opportunity to play alongside his younger brother Theo, who made his Top 14 debut after replacing Cros on the hour mark.
The meeting of two sides with eight European Cup titles between them proved to be one-sided.
Toulon took an early lead through Baptiste Serin's third-minute penalty, but Thomas Ramos quickly responded to level the scores.
It was all one-way traffic from there, as tries from Matthis Lebel, Dimitri Delibes and Emmanuel Meafou put Toulouse 20-3 up at half-time.
Aymeric Luc gave Toulon some hope shortly after the restart with their only try of the game, but Peato Mauvaka secured Toulouse a bonus point.
On Saturday, La Rochelle edged to their second straight win with a 23-21 triumph against Lyon, while defending champions Montpellier bounced back from an opening defeat by beating Bordeaux-Begles 29-19.