Top seed Karolina Pliskova was knocked out of the US Open in the second round with a heavy defeat by France's Caroline Garcia.
Pliskova, runner-up in 2016, lost 6-1 7-6 (7-2) to the world number 50.
Czech world number three Pliskova was the highest ranked player here in the absence of Australian Ashleigh Barty and Romania's Simona Halep.
Meanwhile, other seeds to tumble were Elena Rybakina (11), Marketa Vondrousova (12) and Alison Riske (13).
But there were victories for fourth seed Naomi Osaka, sixth seed Petra Kvitova, eighth seed Petra Martic and Estonian 14th seed Anett Kontaveit.