Top 14 Champions Castres continued their string of positive results against Toulon on Saturday, winning 22-15 at Stade Pierre-Antoine.
Former Springbok flank Juan Smith made his long-awaited return to rugby in the 61st minute off the Toulon bench but it was his countryman, Castres scrum-half Rory Kockott, who stole the limelight with a man-of-the-match performance as the home side recorded their fourth consecutive win in clashes with the European champions.
Three months after winning the Top 14 Final - the last time these clubs met - Castres underlined their status as a bogey team for Toulon and maintained their unbeaten record on home soil this season.
Castres led 13-9 at the interval thanks to a try on the stroke of half time from hooker Brice Mach.
Kockott's boot did the rest as the South African edged a kicking duel with former England pivot Jonny Wilkinson, who kicked all of Toulon's points.
Wilkinson's 15 points ensured RCT picked up the defensive bonus. However, defeat means the league leaders could lose their place at the Top 14 summit later on Saturday if either Clermont or Stade Franšais win at home to Grenoble or Brive respectively.
Toulon had made the early running with two Wilkinson penalties putting them in the ascendancy.
Kockott replied with a penalty of his own before a huge drop goal from halfway levelled the scores, only for Wilkinson to nudge the European champions ahead again with his third successful effort.
But the turning point came just before the end of the first half as Castres got a rolling maul going and Mach burrowed over.
Kockott kicked the extras to send Castres into the interval leading 13-9.
Wilkinson kicked his fourth penalty and then sent a drop goal off the upright and through the sticks to put Toulon back in front, although that lead lasted less than a minute before Kockot landed a penalty.
Two more scores from the trusty boot of the South African ensured Castres held on for victory and moved up to second, level on points with Perpignan and Montpellier.
Pens: Kockott 4
Pens: Wilkinson 4
Castres: 15 Brice Dulin, 14 Romain Martial, 13 Romain Cabannes, 12 Remi Lamerat, 11 Marcel Garvey, 10 Remi Tales, 9 Rory Kockott, 8 Antonie Claassen, 7 Yannick Caballero, 6 Ibrahim Diarra, 5 Rodrigo Capo Ortega, 4 Piula Faasalele, 3 Karena Wihongi, 2 Brice Mach, 1 Yannick Forestier,
Replacements: 16 Marc Antoine Rallier, 17 Michael Coetzee, 18 Richard Gray, 19 Pedrie Wannenburg, 20 Julien Tomas, 21 Seremaia Bai, 22 Geoffrey Palis, 23 Mihaita Lazar.
Toulon: 15 Delon Armitage, 14 Alexis Palisson, 13 Mathieu Bastareaud, 12 Maxime Mermoz, 11 Rudi Wulf, 10 Jonny Wilkinson, 9 Michael Claassens, 8 Chris Masoe, 7 Steffon Armitage, 6 Virgile Bruni, 5 Danie Rossouw, 4 Bakkies Botha, 3 Martin Castrogiovanni, 2 Sebastien Bruno, 1 Xavier Chiocci,
Replacements: 16 Jean-Charles Orioli, 17 Andrew Sheridan, 18 Konstantine Mikautadze, 19 Juan Smith, 20 Vincent Martin, 21 Josua Tuisova, 22 David Smith, 23 Carl Hayman.