British number three Dan Evans missed out on a spot in the Atlanta Open semi-finals after a straight-set loss to big-serving American Reilly Opelka.
Opelka, 21, hit 23 aces on his way to a 7-6 (7-3) 7-5 victory.
After edging the first set, Opelka fought back from 15-40 to break world number 55 Evans’s serve for a 6-5 lead in the second and served out the match to love.
Opelka, ranked 57th, meets Australian Alex de Minaur in the semi-finals.
De Minaur, 20, progressed after compatriot Bernard Tomic retired as he trailed 6-2 3-0 after just 39 minutes.
Tomic, 26, called for the trainer at the end of the first set – seemingly indicating he felt pain in his torso when serving – and eventually decided he could not continue any more.
Earlier this month, Tomic was fined his full Wimbledon prize money of £45,000 for not meeting the “required professional standard” during his 58-minute first-round defeat by Jo-Wilfried Tsonga.