Toulon ensured their qualification for the play-offs of the Top 14 on Saturday, while Brive plunged towards the second relegation spot after losing to Bordeaux-Begles.
Toulon enjoyed a three tries-to-one 25-22 victory over Toulouse, who are already through to the semi-finals of the end-of-season finale with Clermont as the two top finishers.
In the penultimate weekend of French league action, Toulon's win saw them move into third spot, with Montpellier also having qualified for the six-team play-offs after beating Biarritz 21-16 on Friday.
Castres beat Clermont 30-19 to stand in fifth place on 65 points, poised to also advance pending the result of the later Racing-Metro v Stade Francais derby match.
At the other end of the table, Bayonne took a massive step towards survival in the Top 14 with a bonus-point 31-10 home win over Agen.
But there were tears as Brive's 23-9 loss to Bordeaux left the latter safe but themselves in 13th place, five points adrift of Bayonne.
Brive now face the prospect of not only having to win with a bonus point in their final away game at heavyweights Clermont, but also Bayonne losing, without a defensive bonus point, away to Castres.
Lyon, beaten 34-22 by Perpignan, sit bottom of the table and their relegation to the ProD2 has already been confirmed.
In Toulon, Lionel Beauxis and Jonny Wilkinson traded early penalties in a pulsating match played in perfect conditions, the Toulouse man hitting a second before the home side hit back.
Toulon's Australian centre Matt Giteau made a scything break through a porous defence before sending out an inch-perfect pass to Alexis Palisson, the France winger crossing in the corner for a try Wilkinson failed to convert.
Winger Vincent Clerc responded with a well-taken try after a similar miss-pass from Beauxis, who nailed the extras and a 33rd minute penalty for a 16-8 Toulouse lead.
Welsh prop Eifion Lewis-Roberts was bundled over for a timely converted try early in the second-half for the hosts, Beauxis and Wilkinson again trading penalties.
England flanker Steffon Armitage scored the decisive five-pointer, jinking through under the posts after a period of sustained pressure.
Wilkinson converted to make it 25-19 with 15 minutes to play, Beauxis hitting a penalty shortly after, but the home side held out for the victory.