Montpellier are on the brink of sealing a top-two finish after beating Toulon 36-21, while leaders Clermont Auvergne were beaten by Toulouse in the other Top 14 game to be played on Sunday.
Jake White's Montpellier side are eyeing a European and domestic double after beating Harlequins in the Challenge Cup and only need to avoid defeat at Racing 92 next Sunday to seal a place in the semi-finals of the Top 14.
Montpellier lead Toulon and Racing by four points following a deserved victory at Altrad Stadium, with Timoci Nagusa scoring a try in each half after Mickael Ivaldi's early score.
Josua Tuisova and Xavier Chiocci crossed for Toulon to reduce the deficit to 20-15 at half-time, but Demetri Catrakilis scored 12 points with the boot and Francois Steyn added nine from the tee as Montpellier secured a comfortable win.
Toulouse are three points behind Toulon and Racing in fifth spot after seeing off the leaders 22-11 earlier in the day.
Louis Picamoles and Gael Fickou crossed in the first half after Camille Gerondeau scored the opening try for the table-toppers, while Brock James slotted over two penalties to ensure Clermont trailed 13-11 at the break.
Sebastien Bezy, Florian Fritz and Jean-Marc Doussain put penalties through the posts in the second half to give Toulouse breathing space and consigned Clermont to a seventh Top 14 defeat of the season.