Bok flyhalf Morné Steyn missed a vital conversion which would have given Stade Français a play-off berth in the Top 14.
In a tight match against top team Toulon, in which former Cheetahs hooker Michael van Vuuren scored a try in the 77th minute to set up the dramatic finale, it was all down to man who has not had a great deal of game time. He had come on in the 72nd minute, and five minutes later was entrusted with a massive kick, which he sent wide.
Stade have at least secured the seventh position, which gives them a play-off against an English team for a place in the new European Rugby Champions Cup, which replaces the European Cup next year.
The 17-15 victory secured for Toulon the leadership of the league, while Montpellier, thanks to two tries by former Bulls centre Wynand Olivier, earned themselves second place and a break going into the play-offs, with a 44-10 win over Racing Métro.
Clermont will meet Castres and Toulouse face Racing for the right to face the top two.
At least Perpignan's demise ensured the survival of Grenoble, who have recruited Stormers wing Gio Aplon and Sharks scrumhalf Charl McLeod for next year. They went down 38-8 to Toulouse, for whom Jano Vermaak contributed two of their six tries.
Elsewhere in the log, Perpignan battled valiantly, but their 25-22 defeat to Clermont, along with a Oyonnax's point in a defeat at Brive, condemned the former giants to relegation after 103 years in the top flight.
Clermont 25 Perpignan 22
Bayonne 23 Castres 13
Bordeaux-Bègles 54 Biarritz 29
Brive 19 Oyonnax 17
Montpellier 44 Racing Métro 10
Toulon 17 Stade Français 15
Toulouse 38 Grenoble 8
Play-off qualifier fixtures:
Clermont vs Castres
Toulouse vs Racing Métro
Toulon vs TBC
Montpellier vs TBC
Photo: Pascal Pavani/AFP Photo