Alex de Minaur advanced to the Atlanta Open semi-finals, while fellow seed Taylor Fritz also progressed on Friday.
De Minaur benefited from a retirement against fellow Australian Bernard Tomic as he set up a clash with Reilly Opelka.
Third seed De Minaur was leading 6-2 3-0 when Tomic retired due to a hand injury at the ATP 250 tournament in Georgia.
"The less time you can spend on court is always to your advantage. It's going to be hopefully some hot, humid weather, which I was expecting coming into this week," De Minaur said. "I'm happy to be where I am and now onto the next [match]."
Next up for De Minaur is Opelka, who reached his second Atlanta semi after outlasting Daniel Evans 7-6 (7-3) 7-5.
American second seed Fritz, meanwhile, saw off Miomir Kecmanovic 6-1 7-6 (7-1) thanks to 11 aces and no break points faced.
Cameron Norrie awaits Fritz after the Brit overcame Alexei Popyrin 7-5 6-4.Published 27 Jul 2019, 08:00 IST