Home favourite Jo-Wilfried Tsonga continued his good form in Metz by battling back to defeat German Tobias Kamke and reach the semi-finals.
The two-time defending champion is playing his first tournament since a knee injury forced him to drop out of his second-round match at Wimbledon.
He saw all eight of his break point opportunities saved by Kamke in the opening set before the German converted his first against Tsonga to move ahead.
However, the top seed eventually made his pressure pay by fighting back to come through, 4-6 6-3 6-4.
Tsonga prevailed in two hours and nine minutes and he will next take on another German for a place in the final after eight seed Florian Mayer defeated Carlos Berlocq from Argentina, 5-7 6-4 7-5.
Another former champion of the Moselle Open - Gilles Simon, also advanced to the last four.
The second seed and 2010 champion beat sixth seed Sam Querrey 6-4 7-6 (1) in 77 minutes and goes on to face 31-year-old Nicolas Mahut in an all-French showdown.
The World No 79, who has won two ATP World Tour titles this year, reached the last four for the first time since 2008 with a 6-2 6-4 win over Benjamin Becker.