Phillip Kohlschreiber of Germany defeated Robin Haase in straight sets to set up a semi-final appearance with Spaniard Roberto Bautista Agut at the Kremlin Cup in Moscow.
Fourth seed Kohlschreiber saved all six break points against him as he completed a 6-2 6-4 victory in an hour and 19 minutes.
It's the German's fifth trip to Moscow, but the first time he has reached the last four.
Bautista Agut, meanwhile, was up against Lucas Pouille, consigning the Frenchman to a 6-4 6-2 deafeat in 70 minutes after converting four of the five break points he earned.
The other semi-final will see Russian Evgeny Donskoy take on the tournament's top seed Marin Cilic.
Donskoy beat countryman Teymuraz Gabashvili 6-3 6-2, saving all four break points he faced, while Cilic thrashed Andrey Kuznetsov 6-2 6-1.