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
Fourth-seeded Novak Djokovic is two victories away from his 90th career ATP singles title after defeating Karen Khachanov 6-4, 6-3 on Friday in Kazakhstan.
Djokovic finished off a hard-fought first set in style.
Djokovic, who hasn’t dropped a set yet but faced his toughest challenge against Khachanov, will next play second-seeded Daniil Medvedev, who routed Roberto Bautista Agut 6-1, 6-1 in a Friday quarterfinal.
Third-seeded Stefanos Tsitsipas also advanced to the semifinals with a 7-6, 6-3 victory over seventh-seeded Hubert Hurkacz. Tsitsipas will face Andrey Rublev on Saturday.