Fifth-seeded Nick Kyrgios, just minutes before his Japan Open quarterfinal match against third-seeded American Taylor Fritz was expected to start on Friday, withdrew from the event with a knee issue.
Kyrgios also pulled out of the doubles draw, where he and Thanasi Kokkinakis had reached the semifinals.
Fritz advances to the semifinals against seventh-seeded Denis Shapovalov, who defeated ninth-seeded Borna Coric 6-4, 6-3 in the quarterfinals Friday.
Astana Open
Third-seeded Stefanos Tsitsipas advanced to the semifinals in Kazakhstan with a 7-6, 6-3 victory over seventh-seeded Hubert Hurkacz. Tsitsipas will face Andrey Rublev on Saturday.
Fourth-seeded Novak Djokovic and second-seeded Daniil Medvedev were also hoping to advance to the semifinals with victories on Friday. Djokovic, who is looking for his 90th ATP singles titles, faces Karen Khachanov, while Medvedev battles Roberto Bautista Agut.