NEW YORK — Ben Shelton entered his first-round match at the U.S. Open on Monday as a favorite even though he was facing a former Grand Slam champion.

The 21-year-old Atlanta native and No. 13 seed faced Dominic Thiem, who won the Open during COVID in 2020 but is retiring at the end of this season after battling a wrist injury for the past three years. Shelton’s huge serves and ability to capitalize in clutch moments proved the difference in his decisive 6-4, 6-2, 6-2 victory on a sun-splashed Arthur Ashe Stadium court.

Shelton, who a year ago became the youngest U.S. Open semifinalist since Michael Chang in 1992, banged out eight aces against two double faults to advance to the second round where he will meet veteran Roberto Bautista Agut of Spain on Wednesday.

“I love being out here in New York, not much better atmosphere than being here in Ashe,” Shelton told the crowd on court. “Thank you guys, you brought the energy.”

The left-handed Shelton had the honor of playing the tournament’s first match on Ashe ahead of defending champions Coco Gauff and Novak Djokovic as well as former champion Sloane Stephens, who were all scheduled later Monday. He took the court wearing a matching red, white and blue tank top and shorts and enjoyed the support of the home crowd.

“I’m glad that I had the opportunity to open it up with my first match with Dominic,” Shelton said. “Thanks to all of you for coming out.”

He congratulated Thiem on his career accomplishments, which included two French Open finals appearances and a career-high world No. 3 ranking.

“I’m sorry that this is the way it ended but congrats, you have so much to be proud of and so many people who love you out there,” Shelton said.

In the first set, Shelton saved a break point in his first service game and then capitalized on his third set point when Thiem hit a forehand into the net after a long rally. Shelton cranked one ace at 135-mph in the third game.

Shelton seized a 2-0 lead in the second set when Thiem drilled a forehand wide on break point.

“He puts so much pressure on people because his serve is so big and he’s able to get through those games,” said ESPN’s Nick Kyrgios, a former Wimbledon finalist. “If he’s able to just make a few more returns.”

Kyrgios also pointed out that Shelton had “zero hesitation” to serve-and-volley for easy winners if Thiem was standing far back on the service return.

Shelton set up a double-set point in the second with a huge overhead smash and then won the set when Thiem slapped a forehand wide.

With Thiem serving at 2-5 in the third, he sailed a forehand long on match point and the two men embraced at the net.

“It’s a very mature win,” Kyrgios said. “He understands that Thiem’s not at his strongest [and] to go out here and get it done in an hour and 50, always positive to get it done in a Grand Slam as quickly as possible.”

Thiem received polite applause when he walked on the court as fans knew this was his last dance.

The 30-year-old Austrian was never able to return to top form after suffering the wrist injury in 2021, which sidelined him for months and saw him fall to his current ranking of 210 in the world. He was 2-7 in 2024 coming into the Open.

Shelton, meantime, survived and advanced. If he gets past the second round, he could face fellow American and world No. 20 Frances Tiafoe in the third.

A potential matchup with defending champion and 24-time major winner Djokovic looms in the fourth round.

No American man has won a major title since Andy Roddick at the 2003 U.S. Open and Shelton is among the Americans bidding to end that streak. Five American men are ranked inside the top 20 for the first time since 1996.

“The stars just have to align,” Kyrgios said. “If [world No. 1 Jannik] Sinner or [No. 3 Carlos] Alcaraz goes down in the third or fourth round, who knows? Novak is getting older.

“I think Americans have a really good shot now, I really like their chances.”