ISTANBUL (AP) Second-seeded Grigor Dimitrov rebounded from a slow start on Friday to defeat sixth-seeded Jiri Vesely 7-6 (1), 6-1 and advance to the semifinals of the Istanbul Open.

Dimitrov trailed 5-2 in the first set before recovering, saving a set point at 4-5 on the way. He faces third-seeded Ivo Karlovic, who fired 20 aces to overcome fifth seed Marcel Granollers 7-6 (2), 6-7 (5), 6-4.

''With each match, I'm building up a good foundation to play better,'' Dimitrov said.

Fourth-seeded Federico Delbonis is also is the final four after beating eighth-seeded Albert Ramos-Vinolas 7-6 (6), 6-4 to set up a match against fellow Argentine Diego Schwartzman.

After knocking out top-seeded Bernard Tomic, the unseeded Schwartzman beat Damir Dzumhur 5-7, 7-6 (4), 6-2 to reach the semifinals for a second successive year.