US Open 2023: John Isner's 17-year singles career ends in 5-set loss to Michael Mmoh

Aug 31, 2023; Flushing, NY, USA;  John Isner of the United States reacts as he is interviewed after losing his second round match against Michael Mmoh of the United States on day four of the 2023 U.S. Open tennis tournament at the USTA Billie Jean King National Tennis Center. Mandatory Credit: Jerry Lai-USA TODAY Sports
John Isner of the United States is almost to the finish line. (Jerry Lai-USA TODAY Sports)

John Isner's 17-year singles career ended Thursday after his second-round loss to fellow American Michael Mmoh, 3-6, 4-6, 7-6 (3), 6-4, 7-6 (7), at the US Open. The 38-year-old isn't quite finished with tennis, though, as he still has doubles to play.

After the heartbreaker, which lasted just under four hours, he fought tears as he spoke in front of the packed crowd at Grandstand.

"This is why I've worked as hard as I have my whole life, to play in atmospheres like this," Isner said. "I might not win them all, as we know, just like today. To play in front of this crowd and have the support I've had is pretty special."

Fans knew they were witnessing a goodbye and gave him a standing ovation. The former world No. 8 stopped to wave before stepping through the exit.

Isner announced Saturday on social media that he would be walking away from professional tennis after the US Open.

"This transition won’t be easy, but I’m looking forward to every second of it with my amazing family," he wrote. On Thursday, he cited a foot injury and discouragement from his performances as factors in his decision.

Standing 6-foot-10, Isner has left his mark on the sport. A standout during his college career at Georgia, he won the NCAA doubles title in 2005 and the team title in 2007. He went pro in 2007 and continued adding to the résumé in a way even he didn't expect.

"I think I've overachieved. I never imagined myself having this much success for this long," he said in his postmatch interview. "If my results were better this year, I probably wouldn't be speaking to you right now. That just hasn't been the case."

His list of achievements is expansive, including 16 ATP singles titles and a Wimbledon semifinal appearance. Isner was the top-ranked American man for eight seasons. He currently holds the ATP record for career aces, with 14,470, a number that went up by 48 during his final match.

He will be remembered for winning the longest match in professional tennis history. During the first round at Wimbledon in 2010, he defeated Nicolas Mahut in a three-day match that lasted more than 11 hours and required 183 games.

His doubles partner, Jack Sock, also announced he is retiring after the tournament. They have won three Masters 1000-level titles together.