On a rainy night in New York, Osaka was defeated by American Danielle Collins in straight sets — 7-6 (5) 6-3 — while defending champion Emma Raducanu fell to Alizé Cornet.
Raducanu, 19, stunned the world by winning her first grand slam at Flushing Meadows last year, but she’s struggled to find similar form ever since.
The experience and intensity of the veteran Cornet proved too much for her as she was beaten in straight sets — 6-3 6-3.
“Obviously this hurts a bit because it’s my favorite tournament and there’s been a lot of emotions over the past year,” she told reporters after the defeat.
“I’m proud to be able to prove myself every game, every day, knowing that I am pushing myself to get the best out of myself.”
Raducanu will drop down the rankings after a frustrating year that has been plagued by injuries and changes in her coaching staff.
The youngster struggled to come to terms with the entire WTA Tour, but showed flashes of quality that secured her first Grand Slam title just 12 months ago.
Cornet was simply in better shape and is now no stranger to big results at the slams, having previously defeated Iga Swiatek at Wimbledon.
The Frenchwoman now holds the Open era record for most consecutive grand slam appearances, in the previous 63.
“I think I handle my emotions better,” Cornet told reporters after the game. “I think I’m getting old – more mature. You can tell by my results. I’m 32 – better late than never.”
‘She certainly laughed at me last time’
Osaka had a similar experience to Raducanu, but this time through the talented Collins.
The world’s number 19 had never even won a set against Osaka in all of their previous three encounters, but this time passed the four-time grand slam champion.
“If you lose to someone three times, you get a lot of information about what you can do better,” Collins told reporters.
“Because Naomi is the player she is, she definitely laughed at me last time. I just had to learn from that and make adjustments and I think I did.”
Osaka, a two-time US Open champion, went unseeded this year and is currently ranked 44th in the world.
Struggling with momentum and form, she was likely an underdog going into the first round, but despite the defeat, she delivered an impressive performance.
Collins will now face Spanish qualifier Cristina Bucșa in the next round, while Cornet will face Katerina Siniaková.