Top seed and world number one Simona Halep was sent crashing out of the U.S. Open by Estonian Kaia Kanepi, with the world number 44 prevailing 6-2 6-4 in the first-ever main draw match on the new Louis Armstrong Stadium.
Kanepi recorded her second career victory over a world number one, having defeated Caroline Wozniacki in Tokyo in 2011 while Halep becomes the first top seed in the Open era to lose in the first round in Flushing Meadows.
Kanepi takes opening set with brilliant play
It was Halep who was under pressure early on, facing an early break point on her serve. There was nothing she could do when Kanepi produced a masterful lob to take the early lead.
The Estonian is a powerful player and she was dictating play in all phases, holding with ease and building on her strong play. Her backhand was on fire all match and she set up another break chance.
Halep was spraying errors from all over the court and she sent another groundstroke long to give the Estonian a 4-1 lead.
Kanepi continued to play confidently and when tasked to serve out the set, she held to love with a forehand winner to wrap up a crisp opening set.
Estonian fights off Halep challenge to complete upset
A former Top 15 player, Kanepi was looking every bit of it, smashing a forehand winner to claim the early advantage in the second set.
Halep was visibly frustrated, smashing her racket in the second game and she would have further misery heaped on her when the Estonian broke again.
With a double break lead at 3-0, Kanepi showed her first sign of nerves, double-faulting to hand one of the breaks back.
Halep would hold to further reduce the deficit, but a booming serve and a delicate drop shot finish off the game for the Estonian and with it, a 4-2 lead.
Out of seemingly nowhere, the set was back on level terms, Kanepi netting to give back her advantage at 4-4. Halep seemed to find her footing off of the ground, but once again she found the net to give the Estonian a 5-4 lead.
Serving for the match, Kanepi brought the game to 40-15 and sealed the upset in an hour and 16 minutes when Halep sent one final backhand long, the Romanian falling in the first round in New York for the second straight year while Kanepi advances to a second-round match against Jil Teichmann of Switzerland.