Reilly Opelka won a 46-point tie-break - the longest in ATP Tour history - to beat John Isner and reach the final of the Dallas Open.
Second seed Opelka, 24, triumphed 7-6 (9-7) 7-6 (24-22) to set up a meeting with Jenson Brooksby on Sunday.
Opelka, who stands 6ft 11in, finally converted his eighth match point after a run of 26 straight points on serve.
"I lost track. At one point it was 21-all. It's something I've never seen before," he said.
Opelka, 24, and 36-year-old fellow American Isner served a combined 60 aces in a match that lasted two hours three minutes, with neither player facing a break point.