Benoit Paire advanced to the Open 13 semi-finals after upstaging top seed Stan Wawrinka in three sets on Friday.
Two-time grand-slam champion Wawrinka was favourite to reach his second ATP Tour semi-final of the season, having made the final four in Chennai en route to the title last month.
And while he had earned four consecutive wins against Paire prior to the quarter-final clash, Wawrinka was stunned 6-4 1-6 7-5 by the eighth-seeded Frenchman after almost two hours on the indoor courts in Marseille.
Paire had not beaten Wawrinka since 2013, but the 26-year-old broke in the opening game of the match and again as the Swiss star served to force a tie-break in the deciding set.
Through to his first Marseille semi-final, Paire will now meet fourth seed Marin Cilic.
Cilic - runner-up in 2011 - eased into the final four via a 6-3 6-4 victory over Andrey Kuznetsov at the ATP 250 tournament.
The Croatian served his way into his first semi-final of the season, firing down 10 aces as he won 91 per cent of his first service points.
Nick Kyrgios also powered into the semis thanks to a dominant performance against third seed Richard Gasquet.
Maligned Australian Kyrgios needed less than an hour to see off Gasquet 6-0 6-4.
Kyrgios relinquished just six points on serve, while he tallied 17 aces to earn a showdown with second seed Tomas Berdych.
Berdych was a class above in a 6-3 6-4 win over Belgian sixth seed David Goffin.