The No. 6-seeded Gauff, a 19-year-old from nearby in Florida, was critical of herself afterward, saying that her footwork wasn't great, that her mindset was off and that she played too defensively after serving for the victory at 5-3 in the second set on Saturday.

“That's kind of been where I've been messing up in all my matches this year. All the ones I've lost I think I lost because of that. I think it should be more used as a tool in a toolbox than as a weapon,” Gauff said. “I think I have to change my mentality in the game about not relying on that too much because I think sometimes I play a little bit too passive because I know I can get to balls.”

She heard chants of “Let's go, Coco!” from spectators at the hard-court tournament as she overcame a 5-2 deficit in the opening set, then erased a pair of set points for Potapova in that tiebreaker. Gauff grabbed the set on her second chance with a cross-court backhand winner.

The 2022 French Open runner-up then seemed to be pulling away, going up a break in the second set at 5-3. But Gauff eased up and Potapova became more aggressive in their lengthy baseline back-and-forths, taking four games in a row on a sunny afternoon with the temperature above 80 degrees Fahrenheit (nearing 30 degrees Celsius).

When the 27th-seeded Potapova forced a third set with a backhand winner, she dropped her racket, clenched both fists, leaned forward and yelled.

“It was a very tough match. It was very physical and it was very hot out there," Potapova said. "I was trying to stay cool and just fight for every point and (not) think about the score, especially in the second set.”

Gauff briefly went up 2-1 in the deciding set, but would not collect another game. She wound up with 34 unforced errors -- compared to 20 winners -- and was broken six times in a match that lasted more than 2 1/2 hours.

“My mind just wasn't all the way in today,” Gauff said.

When Gauff dumped a backhand return into the net to fall to 1-5 against seeded opponents this season, Potapova covered her mouth with a hand and shook her head. She had been 0-2 against Gauff previously, but now, will move on to face No. 23 Zheng Qinwen in the fourth round.

Zheng beat No. 12 Liudmila Samsonova 5-7, 7-6 (5), 6-3. Other results included No. 3 Jessica Pegula's 6-1, 7-6 (0) win over No. 30 Danielle Collins; No. 20 Magda Linette's 7-6 (3), 2-6, 6-4 victory over three-time Miami Open champion Victoria Azarenka; and 2017 French Open champion Jelena Ostapenko's 6-2, 4-6, 6-3 victory against No. 13 Beatriz Haddad Maia.

In men's action, No. 2 seed Stefanos Tsitsipas, the Australian Open runner-up who is coming off a loss in his opening match at Indian Wells, California, this month, moved on when Richard Gasquet withdrew before they were scheduled to play because of an injured ankle. That means Tsitsipas, who was given a bye like all seeded players, reached a third-round matchup with qualifier Cristian Garin without having played a point yet at the Miami Open.

Garin defeated No. 27 Sebastian Baez 7-6 (2), 6-3, one of several men's second-round contests in which a seeded player lost. Quentin Halys barely got past No. 15 Alex de Minaur 6-7 (5), 7-6 (3), 7-6 (8); Jiri Lehecka eliminated No. 18 Lorenzo Musetti 6-4, 6-4; Mackenzie McDonald edged No. 19 Matteo Berrettini 7-6 (8), 7-6 (5); Lorenzo Sonego beat No. 23 Dan Evans 4-6, 6-3, 6-2; Alex Molcan defeated No. 28 Yoshihito Nishioka 7-6 (5), 1-6, 6-2; and 119th-ranked American qualifier Christopher Eubanks earned his first career victory over someone inside the top 50 by coming back to beat 20th-ranked Borna Coric 3-6, 6-4, 6-2.