Fifth-seeded Nick Kyrgios, just minutes before his Japan Open quarterfinal match against third-seeded Taylor Fritz was expected to start on Friday, withdrew from the event with a knee injury.
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.
Third-seeded Stefanos Tsitsipas advanced to the semifinals in Kazakhstan with a 7-6, 6-3 victory over seventh-seeded Hubert Hurkacz.
Fourth-seeded Novak Djokovic and second-seeded Daniil Medvedev were to play later today. Djokovic, who is looking for his 90th ATP singles titles, faces Karen Khachanov, while Medvedev battles Roberto Bautista Agut.