Toulouse needed a late try to edge past Castres 23-22 in the opening fixture of the new Top 14 season at Stade Ernest-Wallon on Friday.
Trailing by four points going into the final ten minutes of the rematch of last season's semi-final, Toulouse were forced to dig deep but came up with the goods thanks to a try created by mammoth Tongan loose forward Edwin Maka and scored by fellow replacement Timoci Matanavou.
Castres were chasing their first victory in Toulouse in 34 years and looked poised to snatch an upset win when South African scrum-half Rory Kockott - who scored all the CO's points - touched down for an excellent solo try in the 55th minute.
But, in sweltering temperatures at necessitated water breaks, the visitors were unable to hold on as the defending French champs stepped it up a gear thanks to the strength of their bench.
The sides swapped ends at the end of a try-less first half with Toulouse leading 15-9.
Kockott put Castres ahead against the run of play though with 30m dart, escaping the attentions of Vincent Clerc and Clément Poitrenaud.
Both sides were reduced to 14 men when Toulouse flanker Jean Bouilhou and Castres replacement fly-half Pierre Bernard were both sin-binned for dangerous tackles.
With Lionel Beauxis off the field, former All Black Luke McAlister took over the kicking duties for the champions and he cut the deficit to 18-19 with a penalty. Kockott replied with his fifth penalty of the evening to restore his side's four-point lead.
Toulouse weren't done yet though and Maka (the nephew of former Toulouse number eight Finau) showed his power by holding off three defenders before offloading to Fijian flyer Matanavou, who could dive over to maintain Toulouse's two-and-a-half year unbeaten run at home.
Pens: Beauxis 5, McAlister
Pens: Kockott 5
Yellow cards: Bouilhou (Toulouse - 54th min - dangerous tackle) ; Bernard (Castres - 58th min - high tackle); Lamboley (Toulouse - 74th min - high tackle)
Toulouse: 15 Clement Poitrenaud, 14 Yoann Huget, 13 Florian Fritz, 12 Luke McAlister, 11 Vincent Clerc, 10 Lionel Beauxis, 9 Luke Burgess, 8 Louis Picamoles, 7 Thierry Dusautoir, 6 Jean Bouilhou, 5 Yoann Maestri, 4 Gregory Lamboley, 3 Census Johnston, 2 Gary Botha, 1 Gurthro Steenkamp.
Replacements: 16 Christopher Tolofua, 17 Jean-Batiste Poux, 18 Edwin Maka, 19 Yannick Nyanga, 20 Jean-Marc Doussain, 21 Gael Fickou, 22 Timoci Matanavou, 23 Yohan Montes.
Castres: 15 Brice Dulin, 14 Romain Martial, 13 Paul Bonnefond, 12 Romain Cabannes, 11 Marcel Garvey, 10 Remi Tales, 9 Rory Kockott, 8 Antonie Claassen, 7 Yannick Caballero, 6 Ibrahim Diarra, 5 Iosefa Tekori, 4 Matthias Rolland, 3 Karena Wihongi, 2 Marc Antoine Rallier, 1 Saimone Taumoepeau.
Replacements: 16 Mathieu Bonello, 17 Mihaita Lazar, 18 Christophe Samson, 19 Pedrie Wannenburg, 20 Romain Teulet, 21 Pierre Bernard, 22 Seremaia Bai, 23 Michael Coetzee.
Referee: Romain Poite