MIAMI GARDENS, Fla. — The new site for the Miami Open suddenly is missing a lot of star power.

Serena Williams withdrew Saturday, blaming a previously undisclosed left knee injury. Less than two hours later, top-ranked Naomi Osaka lost in the third round to tour veteran Hsieh Su-Wei of Taiwan, 4-6, 7-6 (4), 6-3.

Osaka’s departure matched the earliest ever in the tournament by a top-seeded woman and jeopardized her No. 1 ranking, depending on results next week.

”I feel like I’ve dealt with the stress of people asking me ‘do I have pressure because I have the No. 1 next to my name?”’ Osaka said. ”I thought I was doing fine with that, but I guess I’m not.”

On the men’s side, seeded losers included No. 10 Karen Khachanov, No. 21 Diego Schwartzman, No. 26 Guido Pella, No. 30 Stan Wawrinka and No. 31 Steve Johnson. In a game of inches, the 5-foot-6 Schwartzman lost to 6-foot-11 Reilly Opelka 6-4, 3-6, 6-4.

Also reaching the women’s round of 16 was the 33-year-old Hsieh, who turned pro in 2001 but has achieved the two biggest victories of her career in the past nine months. Her only other win over a No. 1 player came against Simona Halep at Wimbledon last year.

With two-handed groundstrokes from both sides, Hsieh was the steadier player from the baseline against Osaka. When Hsieh closed out match point with a forehand volley winner, she began to cry as the crowd applauded her performance.

Osaka smiled when reminded it was the first time in 64 matches she lost after winning the first set.

”I know—it’s depressing,” she said. ”I was thinking about it right after I lost.”

Osaka, 21, has won the past two Grand Slam tournaments. Williams, 37, still hasn’t won a tournament since the 2017 Australian Open, before she took a break of more than a year to become a mom. She has played only eight matches this year.