Emma Raducanu is still waiting for her first win at the US Open since her memorable 2021 triumph after another first-round exit.
The 21-year-old stunned the world three years ago when she won the title in just her third senior tournament but it has not been a happy hunting ground since.
After a first-round exit in 2022 and missing last year through injury, Sofia Kenin handed out more misery with a 6-1 3-6 6-4 win on the Grandstand court.
It looked like it could be a short outing as Kenin rattled through the first set, but Raducanu made a match of it by sending it to three sets.
A costly service game midway through the decider proved costly as the former champion headed home.
Having played just one tournament since Wimbledon and skipping the Olympics to focus on her preparation for the US Open, she will be desperately disappointed to fall at the first hurdle and questions remain over the direction of her career.
In her defence, it was a tough draw for Raducanu against a former Australian Open winner, who showed some of her best form.
Kenin took a particular liking to Raducanu’s serve and broke three times on her way to a dominant first set.
The Briton had missed three break points of her own in the first set, but made a move at the start of the second by taking Kenin’s serve.
The American recovered the break straight back but a crucial point at 2-2 and 15-15, where Raducanu hit a backhand winner down the line, changed the momentum of the second set.
It helped her break, with Kenin losing her cool by hitting the ball into the backboard. Two brilliant winners saw Raducanu take a second break and the second set in style.
But it all went wrong for the Brit in the fifth game of the decider as she was broken and there was no way back from there as Kenin clinically saw it out.