Canada's Denis Shapovalov and Felix Auger-Aliassime were ousted in quarterfinals at different ATP Tour events on Friday.
The sixth-seeded Auger-Aliassime, from Montreal, lost 6-4, 3-6, 6-3 to No. 2 seed Alexander Zverev of Germany at the Erste Bank Open in Vienna.
Zverev is now 23-2 since losing to Auger-Aliassime in the fourth round of Wimbledon.
The second-seeded Shapovalov, from Richmond Hill, Ont., lost 6-4, 6-3 to unseeded German Jan-Lennard Struff at the St. Petersburg Open in Russia.
Struff is now 5-2 against Shapovalov.
Meanwhile, Dutch qualifier Botic Van de Zandschulp upset defending champion Andrey Rublev 6-3, 6-4 in another quarterfinal at the St. Petersburg Open.
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.
The 26-year-old Van de Zandschulp, who reached the U.S. 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 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.
In Vienna, Jannik Sinner stretched his winning streak on indoor hard courts to 11 matches and 22 sets Friday by beating Casper Ruud 7-5, 6-1 in a quarterfinal.
The seventh-seeded Italian will take on American qualifier Frances Tiafoe for a place in Sunday's final. In the other semifinal, Zverev takes on Spanish teenager Carlos Alcaraz, who upset seventh-ranked Matteo Berrettini 6-1, 6-7 (2), 7-6 (5).
Ruud, who has won a tour-leading five titles this season, led 5-4 in the opening set but the Norwegian lost nine of the next 10 games as Sinner gained control in most rallies.
The win puts Sinner in a favorable position for one of two remaining slots at next month's ATP finals, leapfrogging Hubert Hurkacz and the injured Rafael Nadal into eighth place.
Tiafoe defeated Diego Schwartzman 6-4, 7-6 (6), one day after upsetting top-seeded Stefanos Tsitsipas.
The 49th-ranked American squandered a 5-1 lead in the second set but broke Schwartzman when the Argentine served for the set at 6-5. Tiafoe saved a set point in the tiebreaker before converting his second match point.
-- With files from The Associated Press
