Cyril Baille's late try saved Toulouse's blushes as they beat Oyonnax 20-19 to reach the Top 14 semi-finals.
In Guy Novès' final home game before he takes over as France boss, Toulouse looked dead and buried, but were able to turn things around thanks to their next generation.
A combination of injuries and suspension left them with a replacement front row of two 21-year-old props and a 20-year-old hooker, but it was those youngsters who allowed them to turn things around in the scrum and grab the win.
Toulouse had dominated early on but once Oyonnax grew into the game, they found their rhythm and Hemani Paea's try, combined with the boot of Benjamin Urdapilleta looked set to send them into the last four and a game against Clermont.
But Toulouse, with Toby Flood kicking the points, chipped away at Oyonnax's lead, before Baille's try six minutes from time put them in front for the final time.
With 90 percent possession and a string of penalties conceded by Oyonnax, it was all Toulouse early on. Flood took advantage to put his team into a 6-0 lead but it was slim reward for their start.
While Toulouse didn't have many clearcut chances, they did blow one huge overlap when Louis Picamoles kept hold of a ball when there was a four on two outside him.
Oyonnax just couldn't get their hands on the ball and looked overwhelmed in their first top flight play-off. However they were able to limit the damage and keep Toulouse out before finally settling into the game after 15 minutes.
When Toulouse were caught coming in at the side in a maul, Urdapilleta got his team on the board, before helping his team gain a foothold in the territory battle.
However a dummied lineout from Jody Jenneker saw one chance go begging and Toulouse then came back up the other end with a potentially crucial attack.
After Luke McAlister had sliced clean through in midfield he lost his footing before the final man. Toulouse tried to recycle quickly but Fabien Cibray took out Sébastien Bézy and was sin-binned for his troubles.
Flood slotted the simple penalty but Oyonnax were back in the game and having struggled initially in the scrum, they were able to turn things around to earn a couple of important penalties.
Trusting their forwards they kicked to the corner and after a couple of attempts at a maul, they went to the pick-and-go. In the end it was Paea who was able to burrow over, proving too strong for Yannick Nyanga from that range. With Urdapilleta's penalty it was Oyonnax who led 10-9 at the break.
The second half started as the first had finished, with Oyonnax on the front foot, and Urdapilleta added another penalty to stretch the lead to 13-9.
Things got worse for Toulouse at the next scrum when Neemia Tialata, their only fit tighthead was injured, forcing 21-year-old espoir Dorian Aldegheri into the fray.
He was penalised at the following scrum, allowing Urdapilleta to stretch the lead to seven points with the game seemingly slipping away from Toulouse.
They reacted though, with McAlister again the spark in midfield. The ball was recycled quickly and Nyanga looked to have squeezed over, but after checking with the TMO, he was deemed to have been held up. It was unfortunate for the hosts, with referee Jérôme Garcès blowing up with Thierry Dusautoir in position to dot down.
Toulouse turned things around at the resulting scrum though and Flood made the most of it to knock over his fourth penalty of the afternoon.
Baille was the next young prop introduced by Toulouse, with Novès trusting his young charges, and their turnaround in the scrum continued with another penalty at the set-piece allowing Flood to cut the deficit to a point just before the hour.
The momentum had clearly shifted but a stupid penalty conceded by Patricio Albacete, handling in a ruck as Oyonnax were being forced backwards, allowed Urdapilleta to push the lead back to four at 19-15.
Oyonnax were back in the ascendancy but Toulouse then began an unbelievable sequence lasting more than two and a half minutes through backs and forwards.
With both teams out on their feet, Toulouse finally went over, with Baille twisting his way over in the corner after an interminable passage of play.
Oyonnax tried as hard as they could to come back, but they had run out of gas and couldn't find their way back into Toulouse territory.
As a result, Novès' long reign at Toulouse continues another week, even if he will be officially announced as the next French boss tomorrow.
Next up will be Clermont, a team who Toulouse have struggled against in recent seasons, having lost home and away to them this year.
Meanwhile Oyonnax can take a lot from this season and lose by a single point in Toulouse for the second time having opened their campaign with a similar result. However, they will have to rebuild without head coach Christophe Urios and some key players who will be off over the off-season.
Pens: Flood 5
Pens: Urdapilleta 4
Yellow card: Cibray
Toulouse: 15 Maxime Medard, 14 Vincent Clerc, 13 Florian Fritz, 12 Luke McAlister, 11 Yoann Huget, 10 Toby Flood, 9 Sebastien Bezy, 8 Louis Picamoles, 7 Yannick Nyanga, 6 Thierry Dusautoir, 5 Patricio Albacete, 4 Yoann Maestri, 3 Neemia Tialata, 2 Corey Flynn, 1 Gurthro Steenkamp.
Replacements: 16 Julien Marchand, 17 Cyril Baille, 18 Joe Tekori, 19 Gillian Galan, 20 Yacouba Camara, 21 Jean-Marc Doussain, 22 Yann David, 23 Dorian Aldegheri.
Oyonnax: 15 Florian Denos, 14 Silvere Tian, 13 Pierre Aguillon, 12 Hemani Paea, 11 Alaska Taufa, 10 Ben Urdapilleta, 9 Fabien Cibray, 8 Viliami Ma'afu, 7 Olivier Missoup, 6 Maurie Fa'asavalu, 5 Thibault Lassalle, 4 Leon Power, 3 Marc Clerc, 2 Jody Jenneker, 1 Antoine Tichit.
Replacements: 16 Paul Ngauamo 17 Ruaan du Preez 18 Valentin Ursache 19 Pedrie Wannenburg 20 Yohan Domenech 21 Regis Lespinas 22 Roimata Hansell-Pune 23 Soane Tonga'uiha
Venue: Stade Ernest Wallon, Toulouse
Referee: Jérôme Garcès
Assistant Referees: Laurent Cardona, Thomas Dejean
TMO: Eric Gauzins