World No 1 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 defeat 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-time Grand Slam champion Sabalenka will be American defending Miami champion Danielle Collins, who beat Swiss qualifier Rebeka Masarova 6-4 3-6 6-3.
Former world No 1 Naomi Osaka prevailed 7-6(6) 3-6 6-4 against American wildcard Hailey Baptiste and will play Italian sixth seed Jasmine Paolini, who advanced when Ons Jabeur retired with a left leg injury while trailing 4-3 in the first set.
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.
"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 while Olympic champion Zheng Qinwen advanced with a 6-1 7-6(3) win over Taylor Townsend.
Local hope Ashlyn Krueger stunned 26th seed and former US Open runner-up Leylah Fernandez to set up a meeting with Zheng.
HONG KONG WILDCARD
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.
"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 7-6(2) 7-6(3) to Czech Jakub Mensik.
The match was temporarily suspended when a large crowd of Brazilian spectators, who were waiting to watch Joao Fonseca's clash with Ugo Humbert due next at the same venue, expressed their anger when that match was shifted to the main stadium.
The fans, some of whom had waited for hours at Grandstand, booed as they left the venue, but were delighted when Fonseca later got past Humbert 6-4 6-3.
"I really liked the decision, because I already played my first round there, so I knew how the court was, the atmosphere," said the 18-year-old Fonseca.
"I knew there was going to be a lot of Brazilians. The crowd is super nice. It's an honour seeing a lot of them cheering for me, saying my name every match I win."
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 there are no Indian Wells semifinalists left in the men's draw at Miami.
Hong Kong wildcard 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.