Top seed Dominic Thiem set up a semi-final showdown with Gilles Simon with a hard-fought straight-sets victory over Gilles Muller at the Moselle Open.
World number 10 Thiem saw 16 aces fly past him in Metz, but hit 33 winners and did not face a break point in the 6-4 7-6 (7-5) victory, which took just 82 minutes.
Thiem is well in contention to feature at the ATP World Tour finals and sits seventh in the Race to London rankings.
But he must negotiate his way past Frenchman Simon to reach the final after the two-time champion was a 7-6 (7-2) 6-0 victor against Malek Jaziri.
On the other side of the draw, 2014 champion David Goffin was pushed to three sets by Nicolas Mahut but the second seed dropped just eight points on his first serve as he came through 6-3 6-7 (6-8) 6-4.
Goffin now faces third seed Lucas Pouille, who also survived a scare in his 7-6 (7-2) 4-6 6-3 defeat of compatriot Julien Benneteau.