ISTANBUL (AP) Second-seeded Grigor Dimitrov had to overcome some tough resistance from qualifier Adrian Ungur before coming through 7-5, 4-6, 7-5 for a place in the quarterfinals of the Istanbul Open on Wednesday.

Dimitrov, who reached the semifinals in Istanbul last year, next faces sixth-seed Jiri Vesely, who rallied to beat Roberto Carballes Baena 6-7 (5), 6-2, 6-2.

Fourth-seeded Federico Delbonis defeated Dudi Sela 6-3, 2-6, 6-4 in the second round to also make the quarters, while eighth-seeded Albert Ramos-Vinolas beat Karen Khachanov 4-6, 6-1, 6-0 to advance.

In the remaining first round match on Wednesday, Illya Marchenko defeated Maximo Gonzalez 6-3, 3-6, 6-1.