The defeat was Osaka’s first since February 2020, and it ended any chance of reclaiming the No. 1 ranking this week from Ash Barty, who is in the semifinals.
Osaka won her fourth Grand Slam title at the Australian Open last month, but in five Miami appearances she has never advanced beyond the quarterfinals.
Against the No. 23-seeded Sakkari, Osaka lost 15 consecutive points on her serve to fall behind and blew a 4-1 lead in the second set. She faced a break point on seven of her eight service games.
Sakkari earned her sixth career win over a top-five opponent. She’s still in the tournament only because she saved six match points in the fourth round before beating American Jessica Pegula.
Osaka took a 40-0 lead in the opening game but didn’t win another point on her serve until the second set. When she ended the drought, she received a big ovation from the small crowd, which she followed up with her best stretch of tennis.
But Sakkari rallied. From 40-0 down she won five consecutive points, hitting one last thunderous return to break for a 5-4 lead. She then coolly served out the victory.