Australian ace Nick Kyrgios has withdrawn from the Kremlin Cup with an elbow injury.
The Australian No.3 had been due to play Mirza Basic for a place in the quarter-finals on Thursday.
Instead, the Bosnian will walk into a quarter-final with Russian Karen Kachanov.
It ends another disappointing tournament for Kyrgios after his limp performance at last week’s Shanghai Masters again raised questions about his effort in ATP matches.
In the women’s draw, Anastasija Sevastova reached the semi-finals by beating Russian veteran Vera Zvonareva 4-6 7-5 6-3.
Sevastova, a US Open semi-finalist, will next face Tunisian qualifier Ons Jabeur, who upset eighth-seeded Anett Kontaveit 7-5 6-1.
Jabeur has won six straight matches, including qualifiers. She has never before reached the semi-finals on tour.