NEW YORK (AP) -- Naomi Osaka's 10-match U.S. Open winning streak and title defense are done after she was outplayed in the fourth round by Belinda Bencic and lost 7-5, 6-4 Monday.
Osaka has been wearing a black sleeve on her bothersome left knee and was visited by a trainer after getting broken to trail 3-2 in the second set.
"I was so excited to come on the court. The challenge cannot be bigger (than) against Naomi," said the 13th-seeded Bencic, who will face No. 23 Donna Vekic in the quarterfinals. "I'm really pleased with how I played and how I managed my nerves in the end."
The result under the closed roof at Arthur Ashe Stadium on a rainy afternoon means both defending champions and No. 1 seeds are gone before the quarterfinals at the year's last Grand Slam tournament.
Last year's men's champ, Novak Djokovic, stopped playing in his fourth-round match against Stan Wawrinka on Sunday night because of a painful left shoulder.
Osaka made her breakthrough at Flushing Meadows in 2018, winning her first major championship by beating Serena Williams in a chaotic final that devolved after Williams got into an extended argument with the chair umpire.
Osaka followed that up with a second consecutive Grand Slam trophy at the Australian Open in January. That allowed her to become the first tennis player representing Japan to reach No. 1 in the rankings.
Bencic, who is from Switzerland, showed again that she is a big-match player. She improved to 3-0 against Osaka this season and now has a tour-leading nine victories over top-10 opponents in 2019. Bencic also is 4-1 over her career against top-ranked players.
Bencic is 22, just a year older than Osaka, but her progress was slowed in recent years by injuries, including wrist surgery.
Back in 2014, when she was 17, Bencic became the youngest woman into the U.S. Open quarterfifnals since 1997, when Martina Hingis took the title.
It was Hingis' mother, and then Hingis herself, who coached and mentored Bencic along the way, and she credited them after getting past Osaka.
"I know so much from them, what they've taught me," Bencic said.
Vekic, a 23-year-old from Croatia, reached her first Grand Slam quarterfinal by saving a match point and edging No. 26 Julia Goerges of Germany 6-7 (5), 7-5, 6-3.
"I don't even know how I won this match," Vekic said.
Well, here's how: Goerges served for the victory at 5-4 in the second set, coming within one point of ending things right there. Not only couldn't Goerges convert, but she also double-faulted three times in that game and unraveled from there, wasting a 21-ace effort.
Osaka is more powerful than Bencic and repeatedly used her serve to keep things close, finishing with nine aces.
But it was Bencic's precision that won the day. She made only 12 unforced errors in the entire match, while producing 29 winners.
Her style is similar to the younger Hingis, who won five Grand Slam singles titles.
"I'm just trying to play it a little bit like chess and anticipate," Bencic said.
Playing so crisply, so cleanly, she took balls on the rise and snapped them back, rushing Osaka and not giving her time to respond in kind.
Bencic broke for a 6-5 lead with a forehand volley winner followed by a backhand passing winner, then served out that set. In the second, Bencic conjured up another terrific backhand passing shot off a sharp volley by Osaka to set up love-40, and a double-fault then made it 3-2.