Stade Francais's backrow forward Juan-Manuel Leguizamon was taken to hospital after being knocked unconscious in a high tackle during their 37-16 French Top 14 championship victory over Brive on Saturday.
Stade Francais scored four tries - through Dave Vainqueur, two from Juan Martin Hernandez, and Franck Montanella to secure the offensive bonus point on the way to their fifth win in five matches.
Although the Paris side had numerous absences among the forwards, they dominated Brive, who have yet to secure a win this season.
Stade's captain Pierre Rabadan said afterwards: "The sending off made life easier for us. It opened things up."
Brive manager Laurent Seigne agreed the red card was the turning point of the game. "The red card killed us today," Seigne said. "Up until then we did not particularly feel in any danger."
Toulon had a 15-9 win over Bourgoin, scoring tries through Clement Imbert and new South African recruit Joe Van Niekerk.
The victory however was not under the gaze of coach Tana Umaga however who had had to return to his native New Zealand for personal reasons. It was only Toulon's second win in five matches.
Bayonne won a difficult yet precious 19-15 victory against promoted Mont-de-Marsan.
Bayonne's win put them in second spot behind Stade Francais before Saturday evening's Montpellier versus Perpignan battle where a win for either team would regain second place.
Castres won their first match of the season in a 12-6 victory over Clermont where the match was marked by poor kicking - 2 out of 9 attempts for Castres and 2 out of 5 for Clermont.
New Zealand flyhalf Cameron McIntyre opened the scoring for Castres with a drop goal which gave them confidence following two home defeats this season.