British No 2 Cameron Norrie progressed to the Atlanta Open semi-finals after Nick Kyrgios retired mid-match.
Norrie, world No 73, won the first set 7-5 before the Australian pulled out after struggling with what appeared to be a recurring hip injury.
Second seed Kyrgios had the trainer on court during the opener and after falling 3-0 behind in the second set made his decision to retire, resulting in boos from the crowd.
Norrie will now meet Ryan Harrison, who defeated Chung Hyeon 6-7 (3-7) 6-2 7-6 (7-5), in his second ATP World Tour semi-final appearance after reaching the same stage at the Lyon Open in May.
The Briton has never faced the world No 53 from America but is excited by the challenge.
"It feels great to get into the semis, but not the way I wanted to do it today," Norrie told the ATP's official website.
"I have played really, really well all week. I am looking forward to my match tomorrow against Harrison. It is going to be a battle. We have both played good tennis all week."
Top seed John Isner defeated Mischa Zverev 7-5 4-6 6-1 in his quarter-final encounter and will now face Matthew Ebden, who eased past Marcos Baghdatis 6-3 6-2.
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Our next tennis action comes from the German Open in Hamburg. Watch the action live on Sky Sports Arena from Monday, July 23 from 10am.
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