Dutch qualifier Botic Van de Zandschulp upset defending champion Andrey Rublev 6-3, 6-4 in the quarterfinals of the St. Petersburg Open on Friday.

Van de Zandschulp, ranked 69th, beat the top-seeded Rublev in 1 hour, 33 minutes for his 16th win from his past 19 matches at all levels.

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The 26-year-old Van de Zandschulp, who reached the US Open quarterfinals last month, will play Marin Cilic in the semifinals. Cilic, who won the tournament in 2011, defeated third-seeded Roberto Bautista Agut 6-4, 3-6, 6-3.

American Taylor Fritz will play Germany’s Jan-Lennard Struff in the other semifinal at the hard-court tournament.

Fritz, who celebrated his 24th birthday by beating compatriot Tommy Paul on Thursday, defeated John Millman 6-4, 6-2, and Struff upset second-seeded Denis Shapovalov 6-4, 6-3.