NEW YORK -- Naomi Osaka smacked her racket against Arthur Ashe Stadium's court. Moments later, she chucked her equipment, sending it bouncing and skidding halfway to the net. Then came a full-on spike near the baseline.

Osaka's game was off. Her composure was gone. By the end, the crowd was booing her for taking too much time between points, turning her back to the court.

Soon enough, Osaka's title defense at the US Open was over in the third round with a 5-7, 6-7 (2), 6-4 loss Friday night to Leylah Fernandez, an 18-year-old from Canada who is ranked 73rd and never had been this far in Grand Slam competition.

Osaka? She came in with a 16-match winning streak at majors and four career trophies, all on hard courts. But this was Osaka's first Slam tournament since she pulled out of the French Open before the second round to take a mental health break -- she also sat out Wimbledon, before participating in the Tokyo Olympics, where she lit the cauldron -- and maybe the time off was an issue.

Another possible factor in her failure to close things out while serving for the victory against the left-hander Fernandez at 6-5 in the second set: Osaka hadn't competed since Monday. That's because the woman she was supposed to meet in the second round, Olga Danilovic, withdrew because she was sick.

Osaka, who left the court after seven games to change outfits and put on a highlighter-yellow dress, was quite good down the stretch in the opening set. She grabbed 12 of the last 13 points, including the last nine, with a break at love to go up 6-5, and a hold at love with the help of a pair of aces at 112 mph and 114 mph to end it.

Osaka seemed on track for a similar conclusion in the second set, leading 6-5 and serving. But when she sailed a forehand wide, Fernandez had her first break of the match to make it 6-all.

And so began Osaka's downward spiral. She fell behind 5-0 in the ensuing tiebreaker, missing shots and displaying her frustration as she occasionally has done in the past -- by flinging her racket. Chair umpire Alison Hughes did not sanction Osaka then, although later a warning was issued for hitting a ball into the stands.

More to the point, Osaka was not at her best. She left the court with a white towel draped over her head after the second set and never really got her game going the rest of the way.