It only seemed as if Simona Halep made history Monday in a New York minute. Actually, it took all of 76 minutes for her to become the first No. 1 women’s seed in the history of the United States Open to lose in the first round, falling by 6-2, 6-4 to Kaia Kanepi.

As Halep’s trademark on-court soap operas go, the stunning upset was still swift, almost routine. Kanepi, a 33-year-old Estonian who is ranked No. 44, dominated a sluggish Halep in the first set before halting her rally to 4-4 from 0-3 in the second in the first main-draw match at the new Louis Armstrong Stadium.

How to explain Halep’s tournament being finished before lunch, even if the Romanian has a history of first-round flameouts — 12 in 34 career Grand Slam events — and Kanepi has six major quarterfinals on her résumé, including one a year ago in New York?

[Get live results and analysis from the first day of the 2018 U.S. Open.]

Halep did not cite fatigue, despite runs in consecutive weeks this month to the finals in the Rogers Cup and Western & Southern Open, winning the former and losing the latter before withdrawing from last week’s event in Connecticut. She did not blame the noisy conditions in the otherwise well-received Armstrong Stadium, where open-air walkways and concessions create a continuous din. She did admit that, for whatever reason, “I never play my best tennis” in New York.

True to character, honest as usual in her post-match confessional, Halep suggested it was more the voices in her head that most contributed to the dismal end to a Grand Slam season that began with a heart-wrenching defeat to Caroline Wozniacki in the final of the Australian Open and a long-awaited breakthrough title at the French Open over Sloane Stephens

“Yeah, nerves,” she before adding with a guilty-as-charged smile, “because I’m born like this, I think.”