French Open champion Stan Wawrinka has been forced out of the Moselle Open with an ankle injury.
The Swiss top seed secured a quarter-final clash with Philipp Kohlschreiber by overcoming Dustin Brown on Thursday.
However, the 4-6 6-3 7-6 (7/4) comeback victory came at a cost as Wawrinka twisted his right ankle at the end of the first set - an injury that has now ended his tournament in Metz.
"Unfortunately, I have to pull out because yesterday I twisted my ankle at 5-4 in the first set," he said on www.atpworldtour.com.
"It was painful in the match, but still okay with tape on it.
"But after a lot of treatment last night and some tests this morning, it's dangerous for me to play because the pain is still there.
"So I will have to see a doctor to see if I will be okay in the next few weeks."
Wawrinka's disappointment means Kohlschreiber, the fifth seed, will be the fresher for the semi-final clash with third seed Jo-Wilfried Tsonga.
The world number 17 got the better of compatriot Nicolas Mahut 6-7 (6/8) 6-3 7-5 in two hours and 25 minutes.
Two-time former champion Gilles Simon will take on Martin Klizan in the other semi-final after overcoming Gilles Muller 6-4 6-4.
The second seed withstood 12 aces to break his Luxembourgish opponent in 88 minutes, while Klizan progressed to his third ATP World Tour semi-final of the season by coming back to beat fourth seed Guillermo Garcia-Lopez 4-6 6-3 7-6 (7/4).
Source: PA