Nick Kyrgios produced a trademark tweener to delight fans at the US Men's Clay Court Championship but it could not prevent a three-set defeat to veteran Ivo Karlovic.
The Australian fourth seed's quarter-final party piece in the first set, in which he volleyed the ball from just inside the baseline for a clean winner, was a highlight but he eventually succumbed to 2007 Houston champion Karlovic 3-6 6-2 6-3.
Kyrgios, who served just three aces, appeared to be hampered by his troublesome elbow as the match progressed.
"It's definitely a huge win. I lost against him every match up until now," Karlovic said.
"I'm really happy that I won today."
Karlovic at 39 became the oldest semi-finalist in an ATP event since Jimmy Connors, at 40, in 1993.
The Croatian, who is the tallest player to play professional tennis at 2.11m, will play Tennys Sandgren in the semi-finals after the American accounted for Guido Pella 4-6 7-5 6-3.
In the other half of the draw, the higher-seeded players were beaten by fellow Americans.
Top seed John Isner lost a tough three-set battle to sixth-seeded Steve Johnson 6-7 (4-7) 6-4 6-7 (5-7).
Taylor Fritz upset third-seeded Jack Sock 6-3 3-6 6-4.
