World No. 1 Iga Swiatek got her US Open title defense off to a dominant start Monday, defeating unseeded Rebecca Peterson of Sweden 6-0, 6-1 to kick off the action at Arthur Ashe Stadium.
The four-time Grand Slam champion fired off 20 winners and four aces to set up a second-round meeting with Australian Daria Saville.
Swiatek said that her tank was "pretty empty" after losing in the Montreal and Cincinnati semifinals earlier this month, but she showed no lack of vigor as she opened her US Open campaign with an ace and blazed through the first set.
The Polish player showed only brief signs of vulnerability early in the second set, as she began to accrue more unforced errors and had to claw her way back from triple break point in the first game.
But she reminded the crowd at Flushing Meadows why she has been No. 1 since April 2022 as she hit an unreturnable backhand shot to break Peterson to love in the fourth game, amid a 10-point winning streak.
Peterson, who only produced two winners across the match, never regained her composure and Swiatek pumped her first after closing out the match with a scorching backhand down the line.
"I really wanted to play solid and start [the] tournament with everything that I focused on [in practice]," she said in on-court remarks.
"I just feel happy that with all the pressure and expectations I can just have fun on court."
Also Monday, No. 8 seed Maria Sakkari crashed out of the US Open following a 6-4, 6-4 defeat at the hands of Rebeka Masarova.
Masarova converted all three break-point opportunities she had during the 87-minute encounter to secure her first career win over a top-10 player.
Brazilian Beatriz Haddad Maia proved she was no pushover even when her back was up against a wall as she battled past 2017 champion Sloane Stephens with a 6-2, 5-7, 6-4 victory.
Fourth-seeded Elena Rybakina, last year's Wimbledon champion, defeated Marta Kostyuk of Ukraine 6-2, 6-1.
Roland Garros semifinalist Haddad Maia saved 11 of 15 break points across the match as the American suffered yet another early Grand Slam exit.
While Stephens was left to reflect on a miserable year at the majors, where her best showing was a fourth-round appearance at Roland Garros, Haddad Maia set up a meeting with Stephens' compatriot Taylor Townsend.
After leveling the contest to one set all, Stephens could not absorb the Brazilian's firepower in the third set, where Haddad Maia sent over 20 winners.
"I was expecting a big battle," Haddad Maia said. "I knew that I had to work very hard and try to focus on my game."
Later Monday, Coco Gauff, a 19-year-old from Florida, was expected to be one of the headliners. She was to face Laura Siegemund of Germany, who won the women's doubles title in New York three years ago. Gauff was the runner-up at the French Open in singles -- losing to Swiatek -- and doubles in 2022.
The first round concludes Tuesday.
Reuters and The Associated Press contributed to this report.