Juan Martin del Potro survived a three-hour encounter against Canadian Milos Raonic to book a Miami Open semi-final meeting with John Isner.
The Argentine fifth seed came through 5-7 7-6 (7-1) 7-6 (7-3), in a match that finished at midnight local time.
Former US Open champion Del Potro claimed his maiden Masters 1,000 title in Indian Wells earlier this month and is now on a 15-match winning streak.
Isner eased past South Korean Chung Hyeon 6-1 6-4 to reach the last four.
The big-serving American hit 13 aces to overcome 19th-seed Chung in only 68 minutes.
“I played extremely well and every match I have gotten better and stronger,” said 32-year-old Isner, seeded 14th.
“I know I’m in the semi-finals and I can’t wait to get back on this court. Del Potro is the hottest player on tour right now, hands down”.