Eight-time champion Serena Williams has withdrawn from the Miami Open because of a knee injury.
American Williams reached the third round on Friday by beating Sweden's Rebecca Peterson, only the seventh match she has completed in 2019.
The 23-time Grand Slam winner was set to face Wang Qiang in the last 32 but the Chinese 27-year-old now gets a bye.
World number one Naomi Osaka suffered a shock three-set loss to Hsieh Su-wei, ranked 27th, in their third-round tie.
Williams, who said she was "disappointed", has now withdrawn from two consecutive WTA events, following her retirement from last week's tournament in Indian Wells because of a viral illness.
The 37-year-old last claimed the Miami title in 2015, with her last Grand Slam win coming at the 2017 Australian Open, a triumph which moved her one behind Margaret Court's record of 24 major singles titles.
"I hope to be back next year to play at this one-of-a-kind tournament in front of the incredible fans here in Miami," she said.
Japan's Osaka, 21, has won the past two Grand Slam tournaments - the 2018 US Open and the Australian Open in January - but went down 4-6 7-6 (9-7) 6-3 to Hsieh on Saturday.
"This was a very emotional win for me," said the 33-year-old Taiwanese, who will now face either Caroline Wozniacki of Denmark or Romanian Monica Niculescu in the fourth round.
"Any time you beat one of the top players it is amazing."
World number two Petra Kvitova was tested by Croat Donna Vekic but won 6-4 3-6 6-4 to reach round four.
The Czech two-time Wimbledon champion and third seed had to fight for more than two hours against Vekic.
She will now meet France's Caroline Garcia in the fourth round. Garcia beat German 15th seed Julia Gorges 6-0 7-5.
Indian Wells champion Bianca Andreescu beat eighth seed and world number four Angelique Kerber of Germany for the second time in a week.
The Canadian, who beat Kerber to win her maiden WTA title last Sunday, won 6-4 4-6 6-1 and extended her winning streak to 10 matches.