Wimbledon champion Elena Rybakina survived a spirited comeback from Russian Anna Kalinskaya at the Miami Open on Thursday, progressing to the third round with a 7-5, 4-6, 6-3 win.
Americans Jessica Pegula and Coco Gauff advanced with less complication enjoying straight sets wins at Hard Rock Stadium.
Rybakina is aiming for the 'Sunshine Double' after defeating Aryna Sabalenka to win the Indian Wells final last week and she came into the match on the back of wins in each of the last eight games she has started.
Kalinskaya broke early in the first set but failed to hold serving for the set at 5-4 up and her Kazakh opponent broke again to turn the set around.
The Russian received medical attention between sets and started the second poorly but trailing 4-2 she produced a brilliant cross-court winner to break back.
She broke again with Rybakina going long and wrapped up the set with a magnificent shot down the line to force the match into a deciding set.
It was tight until Rybakina broke in the sixth game, Kalinskaya going for one deep effort too many but the Russian's resilience was evident again as she responded with a break of her own.
But a tiring Kalinskaya was unable to hold her serve and Rybakina saw the match out to set up a meeting with Spain's Paula Badosa.
World number three Pegula got her campaign under way with a confident 6-3, 6-1 second round win over Canada's Katherine Sebov.
With top-ranked Iga Swiatek having withdrawn, American Pegula is among the favourites to challenge for the title.
"I had to adjust my game plan a little bit in that first set and then was able to close it out pretty easily," said Pegula, a semi-finalist in Miami in 2022.
Pegula will face fellow American Danielle Collins in the second round after she beat Bulgarian Viktoriya Tomova 7-6 (7/3), 6-2.
Sixth-seed Gauff, beaten finalist in the French Open last year, saw off Canada's Rebecca Marino 6-4, 6-3, converting five of her nine break points and twice coming back from a break down in the second set.
"It was an up-and-down match honestly. A lot of breaks. I mean, I did well in the returning part, considering she's a big server," said the 19-year-old.
Belgium's Elise Mertens upset eighth seed Daria Kasatkina 4-6, 6-2, 6-2.
After letting a 3-0 advantage slip in the first set, Mertens dominated as Kasatkina struggled physically, needing a medical time-out in the second set.
Spain's Badosa battled to a 7-6 (7/2), 4-6, 6-3 win over Germany's Laura Siegemund while Russian Anastasia Potapova defeated Ukrainian Marta Kostyuk 6-1, 6-3.
Kostyuk, enjoying plenty of support on the small outer court from Ukrainian fans gathered behind national flags, was never able to put her opponent under pressure.
There was no handshake from the two players at the end of the game as they left the court without acknowledging each other. Potapova will face Gauff next.
Three-times Miami Open winner Victoria Azarenka beat Italy's Camila Giorgi 6-3, 6-1 to book her place in the third round.
In first-round ATP action, big-hitting Czech Jiri Lehecka cruised to a 6-3, 6-4 win over Argentine Federico Coria.
Italy's Lorenzo Sonego ended a run of six straight defeats at Masters 1000 level by defeating Austrian former world number three Dominic Thiem 7-6 (9/7), 6-2.
Sonego took a grip on the match by claiming the first four games of the second set taking advantage of a series of unforced errors.
"I wanted to be aggressive on the return and I was very aggressive overall. I've wanted to play closer to the baseline this year," Sonego said. "I like to play in Miami because the conditions are really fast."
Chile's Cristian Garin beat American Marcos Giron 6-4, 2-6, 6-4 and will face Argentine Sebastian Baez next.
France's Richard Gasquet beat Australian lucky loser Christopher O'Connell 6-4, 3-6, 6-1 to set-up a meeting with second-seeded Stefanos Tsitsipas of Greece.
World number one Carlos Alcaraz starts his campaign on Friday against Argentine Facundo Bagnis.