Before the U.S. Open, Medvedev reached three tour finals in August, winning in Cincinnati but losing in Washington, D.C., and Montreal. Borna Coric, seeded fourth in St. Petersburg, faces qualifier Joao Sousa in the other semifinal.
Coric won his quarterfinal 3-6, 7-5, 6-3 against Casper Ruud, who had not won a tour-level match indoors until this week. Sousa upset 2010 St. Petersburg champion Mikhail Kukushkin 7-6 (8), 6-2.
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