HALLE, Germany -- Yuichi Sugita of Japan upset third-seeded Dominic Thiem 6-2, 7-5 at the grass-court Gerry Weber Open on Wednesday.
The 52nd-ranked Sugita forced 13 break opportunities and took three as he advanced to a quarterfinal against American qualifier Denis Kudla.
Kudla defeated Stefanos Tsitsipas 6-3, 6-4 in their second-round match.
Seventh-seeded Kei Nishikori lost 6-2, 6-2 to Karen Khachanov of Russia.
Fourth-seeded Roberto Bautista Agut stayed in control against Robin Haase, winning 6-4, 7-5, and the Spaniard will next face Khachanov.
Defending champion Roger Federer plays Benoit Paire in the second round on Thursday.