Fifth-seeded Nick Kyrgios withdrew ahead of his quarterfinal match in Tokyo on Friday with a left knee injury.
No. 3 seed Taylor Fritz advanced to the Japan Open Tennis Championships in a walkover.
Kyrgios, 27, also pulled out of the doubles draw, where he and fellow Australian Thanasi Kokkinakis had reached the semifinals.
Kyrgios is a seven-time winner on the ATP Tour. He reached the finals at Wimbledon and the quarterfinals at the U.S. Open earlier this year.
--Field Level Media