World number one Simona Halep was swept aside 6-2, 6-4 by 44th-ranked Kaia Kanepi yesterday, the first top-seeded woman ever to lose in the US Open first round.
It was the kind of Grand Slam history Halep could have done without as she tried to expunge the memory of her first round loss to Maria Sharapova at Flushing Meadows last year.
But the Romanian, who broke through for a first Grand Slam title at the French Open this year, had no answer for Kanepi's power.
The Estonian fired 26 winners to Halep's nine, and even her 28 unforced errors weren't enough to derail her challenge as she cut the rallies short and remorselessly punished Halep's second serve.
"I thought I just have to be aggressive and try to stay calm," said Kanepi, whose run to the quarter-finals last year is just one of her six trips to the last eight in majors -- although she has never gone farther.
The victory let some light into a tight quarter of the draw that also includes 23-time Grand Slam champion Serena Williams, seven-time Slam winner Venus Williams and two-time major winner Garbine Muguruza.
Serena, seeking her first major title since the birth of daughter Olympia last September 1, was to launch her campaign in a star-studded opening night session on Arthur Ashe Stadium against Poland's Magda Linette.
Venus faced a potentially trickly opener against former champion Svetlana Kuznetsova, with the sisters looking at a possible third-round meeting.
Defending champion Sloane Stephens, the third seed behind Halep and Caroline Wozniacki, opens her title defense against Russian Evgeniya Rodina.
For Halep it was a swift end to the dream of a second major title to go with the French Open she won in June.
The Romanian, whose number one ranking is not in jeopardy, had no excuses.
"I cannot say much about this match, just that I didn't really feel the ball," Halep said. "But also, she played really strong and pushed me back, so it was tough."
In the men's event, former champion Stan Wawrinka defeated Grigor Dimitrov for the second successive Grand Slam, knocking the eighth-seeded Bulgarian out in the US Open first round.
Wawrinka, the 2016 winner who missed last year's tournament as he underwent two knee surgeries, swept to a 6-3, 6-2, 7-5 victory on Arthur Ashe Stadium to repeat his opening round triumph over Dimitrov at Wimbledon.
"The last time I played on this great court, I won the title so it was great to be able to come back and play again," said the 33-year-old Swiss.
"The level was really high, there were lots of emotions out there.
"It's always tough to play your best in the first round."
Wawrinka, the former world number three, now down at 101, shrugged off having to take a medical time-out early in the third set.
Wawrinka will next face either Ugo Humbert of France or Colin Altamirano of the United States for a place in the last 32.