French champions Racing 92 held on with just 13 players for a crucial 10-8 victory at Toulouse on Sunday that put them in the driving seat for a play-off spot.
Racing had Samoan prop Viliamu Afatia sent-off and New Zealander front-row Ben Tameifuna yellow carded late on but despite Maxime Medard's last-gasp try for Toulouse, former All Black Luke McAlister missed the conversion that would have levelled the scores.
Defeat ended Toulouse's slim hopes of making the top six, meaning they will miss out on the end of season play-offs for the first time in four decades.
"In this complicated, very tight championship, only victory interested us against a team who are going through some difficulties," said Racing backs coach Laurent Labit.
Racing made a fast start helped by a controversial try.
Following a scything break from Maxime Machenaud, South African lock Gerbrandt Grobler was stretching out an arm to dot down in the tackle when Gael Fickou slid in and knocked the ball out of play.
Referee Pascal Gauzere called for a video review and deemed Fickou to have saved a certain try with a deliberate knock-on.
Gauzere awarded a penalty try and sent Fickou to the sin-bin while Dan Carter converted to add to an earlier penalty.
Toulouse regrouped, though, and Portugal scrum-half Samuel Marques knocked over a penalty to send his team in at half-time trailing just 10-3.
Midway through the second period Afatia was sin-binned for a dangerous tackle but after Yoann Huget finished off a move by touching down in the corner, Gauzere asked for video assistance again.
And again the decision went against the hosts as Huget's foot was found to have grazed the sideline a fraction of a second before touching down.
Racing survived the numerical disadvantage but no sooner did Afatia return that he was shown a second yellow card, and thus a red, five minutes later for collapsing a scrum.
Two minutes from the end Tameifuna was also sin-binned for collapsing a scum but despite Medard's score, Racing held on.
- Montpellier romp -
Earlier, Montpellier coasted to a nine-try bonus-point 61-22 thrashing of rock-bottom Bayonne to secure a top six place and keep alive hopes of a top-two finish.
Jake White's team are now just four points behind second-placed Clermont but with a game in hand. If they beat Racing next weekend, while Clermont are in European Champions Cup action against Leinster, Montpellier will go second with two matches to play.
The top two sides in the French league get a bye into the play-off semi-finals, with the next four teams taking part in an extra round.
"Montpellier are sure of a top-six place for the second season in a row," said South African World Cup winning coach White, who will leave the club at the end of the season.
"The first objective of the season, which is to be in the Champions Cup before the arrival of the new coach Vern Cotter, has been achieved.
"Next week it will be a match for the top three, then the following week for the top two."
This match was over as a meaningful contest long before half time with Australian wing Joe Tomane scoring a hat-trick.
Springbok centre Francois Steyn added two tries while his South African compatriot Willie Du Plessis kicked over eight conversions in a personal haul of 21 points.
On Saturday Lyon ended La Rochelle's five-month unbeaten run in an entertaining 29-25 victory that nonetheless left the visitors 10 points clear at the top.
Clermont romped to a nine-try 59-18 victory at Grenoble that condemned the hosts to relegation alongside Bayonne.
Toulon beat Castres 23-14 to almost secure a play-off spot while Stade Francais thumped Pau 51-16 and Bordeaux-Begles won 22-19 at Brive.