Naomi Osaka's 23-match winning streak came to a crashing halt Wednesday as Japan's world number two was stunned 6-0, 6-4 by Maria Sakkari in the quarterfinals of the Miami Open.

Japan's Osaka, playing her first tournament since lifting her fourth Grand Slam title at the Australian Open in February, won just eight points in the first set, failing to manage a single winner.

Osaka broke in the second game of the second set and seized a 3-0 lead before Sakkari roared back to seal a semifinal spot in the prestigious ATP Masters and WTA hardcourt tournament.

The defeat ended Osaka's chance of overtaking top-seeded Australian Ashleigh Barty atop the world rankings this week, a fact she acknowledged may have upped the pressure she was feeling against Greece's 25th-ranked Sakkari.

"It's hard to say," she said of whether that made a difference in the match.

"The last time I was in this (press conference) seat, I wasn't really thinking at all about rankings, but someone asked me that question, so then I did start to ponder about it a lot.

"So maybe unwillingly that put pressure on myself. But I feel like even if it did, I should be able to rise above that," Osaka said.

"This is definitely something that shouldn't bother me as much as it did."

Osaka said she "felt like I was getting there" as she built her lead in the second set.

"I felt that even though it wasn't pretty tennis -- I like to try to play perfectly, but that doesn't really happen most of the time -- so I thought even though it wasn't pretty tennis, I was trying to find a way to win the set,"  she said, adding that she "would need more time to reflect" on just what went wrong.

Sakkari broke Osaka for the second time in the match after trailing 40-0 to seize a 5-4 advantage, then served out to win the match after 69 minutes when Osaka sent a forehand beyond the baseline.

"She has the most wins so far this year so she's in great form -- it meant a lot to me," Sakkari said of the victory, which prompted a scream of delight after the final point.

"I was focused on my returns. I had to mix it up well. Overall, it was a pretty clever match," added Sakkari, who had saved six match points in her fourth-round win over American Jessica Pegula.

Sakkari next faces either Canadian eighth seed Bianca Andreescu or Spain's Sara Sorribes Tormo.

Medvedev seeks semifinal

Andreescu is playing her first tournament in the United States since lifting the 2019 US Open title. The ninth-ranked Canadian was knocked out of the Australian Open in the second round in her first tournament after returning from a 15-month injury absence.

"Just during my cool down I'll enjoy it with my team, then get back to work," Sakkari said of turning her attention to her next match.

Osaka won only 3-of-13 second-serve points in the opening set and had only a 35% accuracy rate on first serves as Sakkari dominated early, taking 13 straight points on Osaka's serve in one stretch.

"I played a great first set," Sakkari said. "I didn't make many unforced errors. I just came out with a good game plan."

Osaka had not dropped a set at love since her last defeat, which came in February 2020 in a Fed Cup match.

But Sakkari had to battle back to overcome Osaka's fightback.

"To be deadly honest, I got a little tight in the first two games of the second set," Sakkari said.

"I had two break points and didn't take them, then a bad service game, which can happen. I stayed within myself and started fighting back, hitting a few more balls and winning a few points against her."

Men's quarter-final action got underway at the Hard Rock Stadium with top-seeded Daniil Medvedev taking on Seventh-seeded Roberto Bautista Agut.

The Spanish veteran has won both prior encounters with Medvedev, who was runner-up to Novak Djokovic at the Australian Open and reached No. 2 in the world with his victory at Marseille in March.

The winner of that match will take on either 21st-seeded Italian Jannik Sinner or 32nd seed Alexander Bublik of Kazakhstan.