World number one Aryna Sabalenka reached the last 16 at the Miami Open when Elena-Gabriela Ruse retired injured on Saturday, while men's top seed Alexander Zverev beat Jacob Fearnley 6-2 6-4 to reach the third round.
Sabalenka, who arrived in Miami fresh off a loss in last week's Indian Wells final, wrapped up the first set 6-1 before Romanian Ruse was forced to retire with a right thigh injury.
Up next for three-times Grand Slam champion Sabalenka will be the winner of Saturday's night match on Grandstand between American defending Miami champion Danielle Collins and Swiss qualifier Rebeka Masarova.
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Naomi Osaka won 7-6(6) 3-6 6-4 against American wild card Hailey Baptiste to set up a clash with Italian sixth seed Jasmine Paolini, who advanced when Ons Jabeur, trailing 4-3 in the opening set, had to retire with a left leg injury.
Osaka, who returned to action in January 2024 after a 15-month break during which she had a baby, said her fitness level is better now than it was in 2021 when she won the most recent of her four Grand Slam titles.
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"I feel like I'm better than 2021. You know, COVID really set me back, I'm not going to lie. I was in the house doing nothing," said Osaka.
"But yeah, fitness-wise definitely the best I've been in a couple of years, for sure."
Third seed Coco Gauff also progressed with a 6-2 6-4 win over Greece's Maria Sakkari.
On the men's side, Zverev looked comfortable against British qualifier Fearnley as the German mixed a solid serve with dominance from the baseline while saving the only two break points he faced during the 74-minute match.
For Zverev, who lost at the first hurdle in Indian Wells, the win gave him a German record 145th Masters 1000 win, one more than Tommy Haas. He now faces Australia's Jordan Thompson.
"Happy to kind of have improved a few things from Indian Wells where I didn't feel well on the court. I didn't feel like I played good," Zverev told reporters.
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"Hopefully this is just the first of many matches for me here and I can continue playing well."
Indian Wells champion Jack Draper crashed out of the Miami Open second round as the sixth seed and British number one fell 7-6(2) 7-6(3) to Czech Jakub Mensik.
Reilly Opelka rallied to beat Danish 11th seed Holger Rune 4-6 6-3 7-6(5) and, with Draper, Carlos Alcaraz and Daniil Medvedev all losing this week, that means there are no Indian Wells semi-finalists left in the men's draw at Miami.
Hong Kong wild card Coleman Wong stunned 13th seed Ben Shelton 7-6(3) 2-6 7-6(5) to advance, while Canada's Denis Shapovalov and American third seed Taylor Fritz also won and will meet in the third round.
