The 22-time Grand Slam winner has been sidelined since January by a left hip flexor injury he picked up at the Australian Open, and has already missed playing at Indian Wells, Miami, Monte Carlo, Barcelona and Madrid.
Elena Rybakina has 46 aces through four matches at the hard-court tournament in Florida and a WTA-leading 201 this season.
Former U.S. Open champions Emma Raducanu and Sloane Stephens were knocked out of the Miami Open on Wednesday, hours after No. 1-ranked and defending champion Iga Swiatek pulled out of the tournament because of a rib injury.
In a three-hour marathon match, Italy's tenth-seeded Jannick Sinner defeated top-ranked Carlos Alcaraz by winning 6-7 (5), 6-4, 6-2 after falling behind in the first set.
The No. 6-seeded Gauff blamed her footwork, mindset, and defensive gameplay in the second set for her loss.
The No. 1-ranked Swiatek was supposed to face Claire Liu in the second round on Thursday, who will now go up against 94th-ranked Julia Grabher.
Top-ranked Carlos Alcaraz took his spectacular arsenal to the highest-ranked American man in Taylor Fritz and blasted into the semifinals with a 6-4, 6-2 victory at Hard Rock Stadium.
