Gilles Simon came from a set down to book his place in the semi-finals of the BRD Nastase Tiriac Trophy at the expense of Poland's Lukasz Kubot.
The top-seeded Frenchman needed over two hours to claim a 3-6 6-1 6-3 victory over the seventh seed and set up a last-four meeting with Matthias Bachinger.
Bachinger beat Daniel Brands 6-4 6-1 in an all-German quarter-final.
The other semi-final will be contested between Italy's Fabio Fognini and Hungarian Attila Balazs.
Fognini fought hard for a 6-4 6-7 (4/7) 6-4 win over compatriot Andreas Seppi, while Balazs, ranked 450 in the world, overcame Xavier Malisse 4-6 6-3 6-4.