Coco Gauff’s attempt to defend her first major title failed amid a barrage of double faults and she lost in three sets to fellow American Emma Navarro.

The result continued the unpredictable history of this US Open, which has already lost its two biggest male stars: Novak Djokovic and Carlos Alcaraz.

Gauff has been the most famous name in American tennis (at least among active players) since Serena Williams last played here two years ago, and she made good on her promise by winning the US Open last summer at just 19 years old.

At the time, Gauff’s breakthrough seemed to mark a turning point in her career and foreshadow a period in which she would win numerous trophies.

A year later, things haven’t worked out quite as well. Although Gauff remains one of the most consistent players on the WTA Tour (she and Jasmine Paolini are the only women to have reached the fourth round of all four majors this season), she has only been able to add one title to her collection, at the relatively unremarkable season opener in Auckland.

Gauff’s ongoing technical problems were all too obvious against Navarro, a clean and consistent hitter who had also knocked her out of the match at the same stage at Wimbledon this summer.

Despite the work of Andre Agassi’s former coach Brad Gilbert, Gauff still regularly loses control of her two most important shots – the forehand and serve. It is only because she is so good in all other areas – backhand, movement, net play and mentality – that she remains a fixture in the world’s top five.

“I don’t think I’ve ever seen her play so badly in a match,” said ABC commentator Chris Evert. The statistics were certainly devastating. Gauff made a massive 19 double faults – nearly five complete games – which contributed to an equally alarming tally of 60 unforced errors.

Gauff’s famous fighting spirit helped her recover from a slow start and tie the match at 1-1, largely through sheer force of will. But she showed her most inconsistent side in the deciding set. Gauff played 35 points on her own serve in the third set, and these were almost evenly distributed between first serves, second serves and double faults.

After the match, Gauff insisted she played well from the ground, but admitted that “I just didn’t serve well.” She went on to explain that she has a technical weakness where the left side of her body snaps down too early when she should be standing upright and reaching for the ball.

When asked if she could emulate world number two Aryna Sabalenka, who hired a biomechanist to restore her failed serve, Gauff said she would consider any option at this point.

“I definitely want to hear other opinions,” she said. “I think sometimes it’s more of an emotional, mental thing, because if I go to the practice court now, I would do about 30 serves in a row. I’ve done that before.”

“But yeah, I definitely want to look at other things because I don’t want to lose games like that anymore.”

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