Saracens salvaged a losing-bonus point at the death as Biarritz edged out the English champions 15-10 in a ferocious Heineken Cup encounter.
An attritional first half ended scoreless after Owen Farrell and Marcelo Bosch squandered several shots at goal.
Biarritz came to life in the second half and scored through Imanol Harinordoquy and Takudzwa Ngwenya to seal the victory. But to the delight of the Saracens coaching staff, Alex Goode squeezed into the corner with the last play of the match to earn a bonus point.
Saracens were dealt a blow in the build-up to the clash after Schalk Brits was slapped with a three-week ban for a dangerous tackle against Treviso, but they could call upon South Africa's World Cup winning captain John Smit for his first start.
The reigning Aviva Premiership Rugby champions were also without Neil de Kock and Richard Wigglesworth, with 19-year-old Ben Spencer handed the number nine jersey. Biarritz were without influential scrum-half Dimitri Yachvili, but still boasted fellow international Harinordoquy and former England star Iain Balshaw.
Biarritz had the first chance to put points on the board but Bosch's penalty drifted wide of the posts. Farrell was also off target with the boot 10 minutes later. Balshaw launched a counter-attack shortly before the half-hour mark to begin a frantic five minutes.
Saracens responded with a James Short break down the left wing but after spreading the ball right, Chris Wyles squandered the overlap. Biarritz enjoyed a sustained period of pressure during the closing stages of the half but were unable to break Saracens' defence as the scores remained 0-0 at the interval.
Charlie Hodgson was unable to continue in the second half due to a leg injury, but Saracens took the lead on 51 minutes with a Farrell penalty. But that brought the hosts to life and they quickly responded with a brilliant try.
Balshaw launched a daring counter-attack from his own line and following good interplay from the Biarritz pack down the left flank, Dane Haylett-Petty fired a perfectly weighted kick to the corner for man of the match Harinordoquy to score.
Biarritz quickly extended their lead with a Julien Peyrelongue penalty and went a step closer to victory after scoring a second scintillating try on 65 minutes. From another counter-attack, USA wing Ngwenya sliced through the Saracens defence from within his own half to score under the posts.
Peyrelongue knocked over the conversion to hand his side a 15-3 lead, but Saracens came fighting back.
Short appeared to have given them a glimmer of hope on 68 minutes but television match official Peter Ferguson adjudged the ball to be held up. But after battling away for the remaining 10 minutes, Saracens got their reward when quick hands released Goode to score in the corner to secure the bonus point. Farrell added the extras to bring the scores to 15-10.