New York, Aug 30 : Sixth seed Ben Shelton was forced to retire from his U.S. Open third-round clash against France's Adrian Mannarino on Friday, shortly before 17th seed Frances Tiafoe also bowed out - delivering a major blow to American hopes of ending a 22-year drought for a men's Grand Slam title.

Shelton appeared to struggle with a left shoulder issue, visibly wincing after a forehand early in the fourth set on Louis Armstrong Stadium. He continued to clutch at the area while getting ready to return serve in the second game, ultimately unable to continue.

"I just did something to my shoulder I don't know what it is. I'm in a lot of pain," Shelton said to his father and coach, Bryan Shelton.

Shelton later told his father it was the 'worst pain' he had ever experienced, before consulting the physio again. Despite the discomfort, he managed to hold his own against the crafty left-hander Mannarino, who delivered flashes of brilliance throughout the match.

Touted as a potential contender to end the long American men's title drought at Flushing Meadows - dating back to Andy Roddick's 2003 triumph - Shelton looked visibly distraught during the changeover, burying his face in his towel as emotions took over. Moments later, he retired from the match, prompting audible gasps from the stunned home crowd.

"When he started having pain, he was leading in the match," said Mannarino, who rallied from a set down to draw level at 3-6 6-3 4-6 6-4 when the match was abandoned.

"He probably would have won. It's unfortunate for him and very lucky for me. I don't really know what to say right now. I suppose I'm happy to get through. I wish him the best."

"I was having good fun on the court there were some long rallies. I lost some of them, won some of them. It was fun to play. Ben's such an amazing player, it was a great match. I was enjoying my time on court, even if I was losing."

Just an hour later, American fans faced another tough blow as Frances Tiafoe, a Flushing Meadows mainstay since 2019, suffered a straight-sets defeat - 6-4, 6-3, 7-6(7) - to Germany's Jan-Lennard Struff on Grandstand.

Struff, despite a late bout of double faults, held his nerve in the closing stages to eliminate last year's semi-finalist and deepen the disappointment for the home crowd.

"I think everybody knows sometimes it's tough to serve out the match. I tried to stay calm and tried to refocus and I managed to get some energy back so I was very happy about that," Struff said.

With the exits of Shelton and Tiafoe, Taylor Fritz now stands as the leading American hope at this year's final Grand Slam. He defeated Jerome Kym to reach the fourth round to keep home hopes alive at Flushing Meadows.

/IANS