NEW YORK, NY, USA - Top seed Simona Halep’s US Open campaign was cut short in the first round at the hands of an inspired Kaia Kanepi, who needed just two sets to score first big upset of the US Open, 6-2, 6-4.

World No.1 Halep came into the tournament flying high after a string of big results during the US Open series, lifting the title in Montreal and reaching the final in Cincinnati - which resulted in the Romanian clinching her ranking through the end of the fortnight.

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Kanepi, ranked No.44 in the world, reached the quarterfinals here last year - equalling her best result at Grand Slam level - but has struggled to find her form after suffering from illness and injuries, and hadn’t won back-to-back WTA main draw matches since the 2018 Australian Open.

“I think it's the way we match up,” Kanepi said, recalling her previous match against Halep in 2014 Doha. The Estonian was two points away from victory that day before Halep completed the comeback. “I remembered how I played her last time. I was just trying to do the same today.

“She has been playing really well in U.S. lately, so I thought I just have to be aggressive and try to stay calm. That's what I should do.”

But it was the 33-year-old Estonian who was the fresher player on Monday, playing the first match of the day against Halep on the brand new Louis Armstrong Stadium. She fired 26 winners past Halep’s nine, and far outpaced her own 28 unforced errors.

Kanepi’s flat groundstrokes kept Halep far behind the baseline, and she was quickly rewarded with a break at 2-1, smothering her opponent’s game to extend her lead another break to 4-1.   

Halep finally halted the Estonian’s five-game run to grind out a crucial hold for 5-2 with a handful of perfectly placed forehands to extend her stay in the set. But it seemed like there was nothing Halep could to trouble her opponent, who methodically marched to a love hold to take the opening set off the World No.1.

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Kanepi, who is now 6-0 when she wins the first set against a Top 10 player at a Grand Slam, kept the momentum rolling in the second set. With Halep on the back foot, Kanepi peppered dropshots into her game and rushed the net to much success, and quickly earned a 1-0 lead.

With Kanepi closing in on the match at 3-0, Halep finally found her range to convert her first break point of the match and narrow the gap to just one break and leveled the set a few games later at 4-4. But Halep struggled to stay calm against the unruffled Estonian, who got right back on track with another break to seal the victory over the World No.1.

“Today I just lost. I didn't play great, but she played really well,” Halep explained to press. “I knew that she can play well here. She played quarterfinals last year. I didn't find the balance today. I couldn't play better. So that's it.

“It just was a bad day. And I never play my best tennis here, even if I did quarterfinals, semifinals. I just say that I don't really feel 100% my game when I step on the court here. But maybe in the future it's gonna change something, I will change something and it will be better.

Up next, will face Jil Teichmann, who made a successful main draw debut winning 6-3, 6-0 against Dalila Jakupovic earlier in the day - the first completed match win of the US Open fortnight.

“I love playing here in New York. I have always loved it,” Kanepi enthused. “I think the courts suit my game, and I love being in New York. I like the city. I like the atmosphere in tournaments and in the city, also. And I like the weather: humid and hot.”