Montpellier could be docked five log points after coach Jake White played suspended lock Jacques du Plessis against Stade Français.
Montpellier had already progressed to the playoffs before the final round, but Stade needed a victory to finish in the top six ahead of city-rivals Racing 92.
Stade lost 27-26 to Montpellier, but shortly after the game the club confirmed it had lodged a complaint against Montpellier after White brought on Du Plessis as a substitute. The lock was supposed to serve a one-game suspension following three yellow cards in his previous three games.
It is believed the match officials missed the error because Du Plessis’ name was not on Montpellier’s team-sheet and that White only added him to the bench prior to kick-off.
If Stade’s complaint is successful, they will get five logs points. But while such a points-reversal will have no impact on Montpellier’s position on the log (they finished third), it will send Stade into sixth position ahead of Racing, who would miss the playoffs.
It would be another dramatic twist involving the two Paris clubs this season, following the aborted merger earlier this year and last weekend’s heated derby, which Stade won 27-23.