The big-serving Isner, who famously took part in the longest tennis match ever played at the 2010 Wimbledon Championships, announced last week his plans to retire after the US Open.

NEW YORK: John Isner brought the curtain down on his tennis career Thursday in a five-set loss to fellow American Michael Mmoh in the second round at the US Open.

The 38-year-old Isner surrendered a two-set lead as world number 89 Mmoh saved a match point and came back to win 3-6, 4-6, 7-6 (7/3), 6-4 and 7-6 (10/7) in just under four hours.

"It's tough," said an emotional Isner, who buried his head in his towel while soaking up the adulation of the Grandstand crowd.

He said, "This is why I've worked as hard as I have my whole life, to play in atmospheres like this. Of course, I don't win them all, as we know. Just like today, to play in front of this crowd, and to have the support I have, is pretty special. So thank you."

The big-serving Isner, who famously took part in the longest tennis match ever played at the 2010 Wimbledon Championships, announced last week his plans to retire after the US Open.

He was a quarter-finalist at Flushing Meadows in 2011 and 2018, the same year he also reached the last four at Wimbledon.

Isner departs as the ATP Tour's all-time leader in aces with 14,470.

John Isner's singles career comes to an end. And the appreciation was evident on Grandstand. pic.twitter.com/DwyKReOVTE

— US Open Tennis (@usopen) August 31, 2023

He was the top-ranked American in the year-end rankings for nine straight years from 2012-2020 and finished inside the top 20 in the world rankings for a decade from 2010-2019.

Isner has won 16 ATP singles titles -- including the 2018 Miami Masters -- and eight doubles titles. He was a US Davis Cup regular, posting 15 singles victories and two doubles victories in 18 appearances in the international tournament.

But it is arguably his record-breaking epic with Mahut at Wimbledon for which Isner will be best remembered, as he won the fifth set 70-68 to conclude an 11-hour epic spanning three days.

"I want to give a massive congrats to John. Unbelievable career. Obviously, this is a special moment for me but even more special for John," said Mmoh, who matched his best Grand Slam run.

"Everything he's done the last 20 years. He's been top 20 for 10 years in a row. Stuff like that isn't easy to do."