Simona Halep was the first big casualty at the US Open when she was sensationally beaten by qualifier Daria Snigur on day one.
Halep arrived at Flushing Meadows as one of the favourites to win the title after she was crowned Canadian Open champion this month.
The two-time grand slam champion fell at the first hurdle, though, as Ukrainian Snigur consigned her to a stunning 6-2 0-6 6-4 defeat on Louis Armstrong Stadium.
Making her first appearance in the main draw at a major, the unheralded 20-year-old was rewarded for a positive approach, winning eight out of 12 points at the net and breaking five times.
Halep swept the world number 124 aside in the second set, but the outsider claimed the upper hand with break in the first game of the decider and went on to open up a 5-1 lead.
The former world number one showed her fighting spirit to hang in there, reducing the deficit to 5-4, but Snigur demonstrated nerves of steel to serve out the match and looked as shocked as anyone after sealing her place in the second round in New York.
Halep paid the price for 30 unforced errors, crashing out after a run to the semi-final in the last major at Wimbledon.