Jessica Pegula has been Karolina Pliskova's nemesis this month in the Middle East, and the No.29 seed continued to dominate their rivalry in the third round of the Miami Open with a 6-1, 4-6, 6-4 win in two hours and nine minutes.

Pegula beat Pliskova for the third time in the pair's past three tournaments. The American was a 6-3, 6-1 victor in the Doha quarterfinals and won even more emphatically in the Dubai third round 6-0, 6-2.

"I played her a lot the last three weeks, three tournaments," Pegula said in her press conference. "I kind of expected her to play well there. Even when I was up I still felt like she could easily come back just because she plays so aggressive and she serves well."

In a match of three parts Sunday, Pegula needed to come from 2-4 down in the deciding set to reach the Miami fourth round for the first time.

"I knew it could switch at any second, and it did," Pegula said. "She played really well, and maybe I got a little passive, but I think it was more mental today in that third set to come back and to break.

"I thought I stepped it up and hit some good winners, too. Just happy I was able to get through it mentally."

Initially, Pegula picked up where she had left off. She repeatedly left Pliskova flat-footed with clean strikes into both corners, and read the No.6 seed's serve with ease. Having committed just two unforced errors in an immaculate first set, Pegula raced into a 6-1, 4-1 lead.

At that point, though, Pegula's concentration lapsed. Overpressing off the ground, her game became error-strewn. A double fault gifted the break back, and a forehand long saw the Australian Open quarterfinalist fall behind 4-5. Sensing opportunity for revenge, Pliskova began landing more of her first serves and levelled the match.

The pattern continued deep into the decider. From 1-4 down, the Czech would win nine of 11 games, dominating the middle section of the match and advancing to 4-2 in the third set.

Pliskova held a point for a 5-2 double-break lead. But in the nick of time, Pegula rediscovered her form. A nifty dropshot staved off the break point, and Pegula closed out the hold with consecutive clean winners.

That would be the start of the final momentum shift as the dynamic of the first set returned. A rejuvenated Pegula reeled off the last four games to set up a last-16 clash with No.23 seed Maria Sakkari. The Greek player was ruthless in dismissing qualifier Liudmila Samsonova 6-0, 6-1, the fourth WTA main draw victory of her career in which she has dropped just one game.

"I think we played on grass, and I think she killed me," Pegula said with a smile, looking forward to her match with Sakkari. "I'm playing much better now. I know she's been playing pretty well and kind of solidified her as a really good top player, dangerous, amazing athlete. It will definitely be tough."

Elsewhere, Sara Sorribes Tormo continued her superb form with an extremely on-brand 6-1, 3-6, 6-2 upset of No.21 seed Elena Rybakina in two hours and 24 minutes. It was the Spaniard's ninth three-setter of the year, including three of the 20 longest matches of 2021 so far.

With an 18-4 record under her belt, including her maiden title in Guadalajara this month, Sorribes Tormo is proving to be one of the toughest players on tour to hit through. Her defences defused Rybakina's power completely in the first set, and the Kazakh had few answers. Racing forwards to conjure up a series of brilliant passing shots, Sorribes Tormo advanced to a 6-1, 2-0 lead.

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To her credit, Rybakina buckled down and adjusted her strategy to turn the match around for a set. Rallying with greater patience before unleashing her full power, the 21-year-old finally captured the Sorribes Tormo serve with a passing shot of her own, and the break back paved the way to an impressive second-set fightback.

But cheap Rybakina errors returned with a vengeance as the decider got under way, and she was unable to catch up after her poor start. In a match with no shortage of break point opportunities, Rybakina's performance on them was crucial: she would win just five of the 17 she carved out, frequently failing to put away sitters. By contrast, Sorribes Tormo converted eight of her 15 chances to make her debut in the last 16 of Miami.

"I still don't believe it," Sorribes Tormo said afterwards. "When you play against this kind of player and they are hitting bombs, I try to stay all the time inside the court. Don't lose the court, go against her, try to play as long as you can - it worked. The most important thing is that I'm doing exactly the same. I'm doing nothing different for the past year. Now it's coming together. I'm playing the whole match the same level."

No.2 seed Naomi Osaka also progressed to the fourth round of Miami for the first time, after qualifier Nina Stojanovic withdrew ahead of their Grandstand clash due to a right thigh injury.

2021 Miami Highlights: Sorribes Tormo's passing shots defeat Rybakina