Daniil Medvedev defeated Russian Karen Khachanov 6-3, 3-6, 6-3 at the Vienna Open to set up a mouthwatering semi-final clash with Stefanos Tsitsipas.
Dominic Stricker was the first to cause a major upset at the US Open when he knocked out seventh seed Stefanos Tsitsipas.
The US Open singles draws were announced on Thursday, revealing a host of tantalising opening round matches.
American Chris Eubanks stunned world number five Stefanos Tsitsipas to reach the quarter-finals of Wimbledon with the biggest knockout of his career.
Stefanos Tsitsipas survived a five-set thriller against Dominic Thiem to set set up a second-round clash with British hopeful Andy Murray at Wimbledon.
Stefanos Tsitsipas has defended himself from accusations of racism over comments he made about Nick Kyrgios at last year's Wimbledon.