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,”
The other men’s quarter-finals will be played on Thursday when South African sixth seed Kevin Anderson faces Spanish 16th seed Pablo Carreno Busta, before German fourth seed Alexander Zverev takes on Croatian Borna Coric.