Holders Saracens suffered defeat in the opening match of their Heineken Champions Cup title defence after going down 30-10 to Racing 92 at the Paris La Defense Arena.
The reigning Premiership and European champions, who are set to drop their planned appeal against a £5.4million fine and a 35-point penalty for a breach of the salary cap, were comfortably beaten as Racing claimed a bonus-point victory.
The hosts ran in four tries through Virimi Vakatawa, Teddy Thomas, Finn Russell and Wenceslas Lauret, with Maxime Machenaud kicking 10 points.
Alex Lozowski scored the only try for a Saracens side missing a host of star names, with scrum-half Ben Spencer contributing five points with the boot.
Racing, who were beaten by Saracens in the 2016 Champions Cup final, started the game on the front foot with Machenaud nudging them ahead with a successful penalty after a period of early pressure.
The French outfit then claimed the first of their tries in the 10th minute as Camille Chat carried over the gainline deep in the Saracens' 22 before Machenaud's pass put Vakatawa over for the score.
Sarries' only real attack in the first half came when full-back Matt Gallagher showed terrific pace to get into the Racing 22. The Saracens forwards tried desperately to force their way over the try line but the ball was eventually turned over by Chat.
Otherwise, Racing were in complete control with Machenaud adding a further three points from the kicking tee.
Spencer finally put Saracens on the board after 23 minutes with a long-range penalty from just inside his own half but Racing further extended their lead moments later.
A half break from Scotland international Russell opening things up for the hosts with Thomas eventually crossing at the far right-hand corner despite the best efforts of Lozowski.
Juan Imhoff very nearly claimed a third Racing try on the stroke of half-time but Vakatawa's pass was deemed to be forward, meaning the hosts turned around 18-3 ahead.
Racing were back on the attack at the start of the second half but Saracens were given hope with Nick Tompkins stealing the ball from Russell on halfway. Tompkins raced forward into the Racing 22 before drawing his man to put Lozowski over for a try, which Spencer converted to make it 18-10.
However, any hopes of a comeback were short-lived as Russell exploited a massive hole in the Saracens defence before gliding his way over with Machenaud adding the extras.
Racing now had the bit between their teeth and they claimed the try bonus point with France international Lauret crashing over from short range off the back of a powerful driving lineout.
With the result beyond doubt Racing laid siege to the Saracens try line during the final quarter of the game as they chased further tries.
Saracens' cause was further hit when replacement scrum-half Tom Whiteley was sent to the sin bin for taking Teddy Iribaren out without the ball.
From the resulting scrum Racing's powerful number eight Antonie Claassen was held up over the line and, despite applying relentless late pressure, the home side failed to breach Saracens' try line for a fifth time.