American Coco Gauff was knocked out of the Miami Open on Saturday after an intense three-set battle with Anastasia Potapova while Indian Wells champion Elena Rybakina earned a hard-fought comeback win against Spain's Paula Badosa.
Three-times Miami winner Victoria Azarenka fell to Poland's Magda Linette but third seed Jessica Pegula advanced with a 6-1, 7-6 (7/0) win over fellow American Danielle Collins.
Potapova showed determination, stamina and some powerful baseline hitting as she beat South Florida-based Gauff, the world number six, 6-7 (8/10), 7-5, 6-2.
The two hour, 41 minute match in the early afternoon heat ebbed and flowed before Potapova took a firm grip in the third set.
The 27th-seeded Russian led 5-2 in the first set but Gauff fought back to win the tie-break after Potapova went wide with a poor shot on set-point.
Gauff looked to have the momentum and served for the match at 5-3 up in the second set but with nothing to lose, Potapova changed gears and her free-swinging approach paid off with her winning the next four games.
After a 10 minute heat break, Potapova returned looking fresh and confident but Gauff was struggling to refind her rhythm and after Potapova, ranked 26th, broke in the fifth game the outcome never looked in doubt.
The win was Potapova's third career victory against a top 10 opponent and her first against Gauff after two losses.
"I think I just let it go, and I started to focus on my tennis and going for my shots and not thinking what she is going to do," Potapova said of her turnaround performance.
Gauff was disappointed with a performance where she failed to find a consistent rhythm.
"I felt like I just didn't play how I wanted to today. Really, where I got in the match was just because of my mentality, but not because of my game," said the 19-year-old, who said that while she felt some nerves on her home court, she wasn't over-awed.
"I don't think that's the reason why I lost today. I really think it was a combination of Anastasia playing well and me not stepping into the court when I needed to in certain moments," she said.
Potapova will play Chinese starlet Zheng Qinwen in the round of 16 after she beat 12th seed Liudmila Samsonova 5-7, 7-6 (7/5), 6-3 in 3 hours and 7 minutes.
Rybakina rallied from a set down to sink Badosa 3-6, 7-5, 6-3. She extended her winning streak to 10 matches as she kept on course to claim the Miami-Indian Wells "Sunshine Double".
The Kazakh struggled in the first set with Badosa breaking her serve four times and although she got her game together in the second set, she found herself 5-4 down and facing match point.
That proved to the momentum swing in the contest as Rybakina held serve and then broke the Spaniard to see out the set and she was in full charge of the third set.
"It didn't start well in the first set but in the end I just found some energy," said Rybakina.
"It was a really tough battle. I was trying to focus on every point because the first set didn't go my way, but it was just a few mistakes here and there. Overall, I played well," she said.
Azarenka fell in three sets to the lower-ranked Linette 7-6 (7/3), 2-6, 6-4 ending her hopes of a fourth Miami title.
Linette, who had not won a set off of Azarenka in their two prior meetings, converted five of her eight break points and will now face Pegula for a place in the quarter-finals.
Former French Open winner Jelena Ostapenko defeated 13th seed Brazilian Beatriz Haddad Maia for the fourth time in as many meetings to reach the fourth round with a 6-2, 4-6, 6-3 win.
Pegula advanced to the fourth round with a 6-1, 7-6 (7/0) win over fellow American Danielle Collins.