NEW YORK -- Once a sure bet to stick around for a while at Grand Slam tournaments, Sloane Stephens suddenly can't even win there.
The 21-year-old American had her earliest loss at the U.S. Open, upset in the second round Wednesday by 96th-ranked Johanna Larsson.
Down a set and a break, Larsson rallied to win 5-7, 6-4, 6-2 to match her best performance at a major tournament. The 26-year-old Swede had been 0-4 at Flushing Meadows before this year.
When the match ended with her 63rd unforced error, the 21st-seeded Stephens was in such a hurry to leave Arthur Ashe Stadium that she briskly walked around the net to Larsson's side of the court for the handshake.
As Stephens had climbed the rankings, the knock on her was that she would shine in the big-time tournaments and slump in other events: Her Grand Slam record coming into Wimbledon this year was 32-12, while she's 58-57 everywhere else.
Stephens reached at least the fourth round at six straight major tournaments starting with the 2013 Australian Open, when she stunned Serena Williams to make the semifinals. The longest active streak at the time, it ended with a first-round loss at Wimbledon this summer.
Now her stay at her home Grand Slam event is over quickly after she had advanced to at least the third round in three previous trips to the U.S. Open.
On the verge of breaking into the top 10 last fall, Stephens has slid to No. 24 in the rankings.
"Everyone goes through times like this," she said. "I'm not the first person and won't be the last."
Larsson has now reached the third round at a major tournament twice this year after breaking through at the French Open.
"I just was trying to really tell myself to go for it," she said. "You won't win matches by holding back. Also, a lucky shot every here and there."
Her victory was the second big women's upset of the day. Peng Shuai beat fourth-seeded Agnieszka Radwanska, the first top-10 player knocked out of the tournament.
The 39th-ranked Peng won 6-3, 6-4, giving China a big win in the tournament with third-ranked Li Na out with a knee injury.
"It's an amazing time for me," Peng said.
The U.S. Open is the only Grand Slam tournament in which Radwanska, the 2012 Wimbledon runner-up, has failed to reach the quarterfinals.
"I really want to know the answer," Radwanska said. "Then maybe I will find a way to play better here and just try another way to be in the second week."
Peng had been 3-22 against top-five opponents, the last victory coming in 2011. That year was also the last time the 28-year-old made the third round at the U.S. Open.
On Wednesday, she won a 27-point rally with a sizzling backhand winner down the line to set up her third match point, then clinched victory with another backhand winner deep into the corner.