New York - World number one Simona Halep says there's no mystery to her historic first-round failure at the US Open on Monday.
"I just lost," the top-ranked Romanian said after she was blown off the Armstrong Stadium court 6-2, 6-4 by big-hitting Estonian Kaia Kanepi.
"I didn't play great, but she played really well," said Halep, who became the first top-seeded woman ever to lose in the first round of the US Open in 50 years of professional-era tennis.
The mercurial 26-year-old was buoyed this year by her first Grand Slam singles title at Roland Garros.
Although that was followed by a third-round exit at Wimbledon, she impressed in the hardcourt build-up to the US Open with a victory in Montreal and a run to the semi-finals at Cincinnati - where fatigue was a factor in her shock loss to unheralded Kiki Bertens of the Netherlands.
After a week off Halep was raring to go at Flushing Meadows, aiming to expunge the memory of a first-round loss to Maria Sharapova last year.
But it was another "one and done" for Halep in New York.
"Today just was not my day," Halep said "The balance was not there. I couldn't feel myself strong on the court to win this match."
Halep said when the draw was revealed last Thursday that coach Darren Cahill had warned her the opening clash against 2017 quarter-finalist Kanepi would be tough.
The Estonian, ranked 44th in the world, seized control with a run of five straight games for a 5-1 lead in the opening set, breaking Halep twice and serving it out in just 28 minutes.
Two early breaks saw Kanepi up 3-0 in the second before Halep, with the New York crowd behind her, battled back to level the set at 4-4.
She was one point from holding serve for a 5-4 lead, only to drop her serve and give Kanepi a chance to serve for the match, which she did wihtout a hitch.
"I fought for every ball," said Halep, who received a warning in the second set after twice slamming her racquet down in frustration.
"I missed three balls, easy balls at 4-All, 40-15. So it's on me. I couldn't take that game, and then she served pretty well. So, yeah, I'm a little bit disappointed that I didn't make that game. Maybe I could take that second set and then you never know."
But Halep, who at least has the comfort of knowing her number one ranking is secure, insisted the defeat wouldn't haunt her.
"It's not a drama," Halep said. "It's just a day. It's a bad day for me. But also, she deserved to win because she was playing better than me today. So it's nothing about pressure. It was just a day."
US Open results on Monday, the first day of the 2018 tournament at Flushing Meadows (x denotes seeded player):
Karen Khachanov (RUS x27) bt Albert Ramos (ESP) 6-3, 6-2, 6-3
Jack Sock (USA x18) bt Guido Andreozzi (ARG) 6-0, 7-6 (7/4), 6-2
Guido Pella (ARG) bt Casper Ruud (NOR) 6-4, 6-4, 6-1
Paolo Lorenzi (ITA) bt Kyle Edmund (GBR x16) 4-6, 6-4, 7-5, 6-1
Milos Raonic (CAN x25) bt Carlos Berlocq (ARG) 7-6 (7/4), 6-4, 1-6, 6-3
Gilles Simon (FRA) bt Lloyd Harris (RSA) 6-2, 6-2, 6-3
Stan Wawrinka (SUI) bt Grigor Dimitrov (BUL x8) 6-3, 6-2, 7-5
Kaia Kanepi (EST) bt Simona Halep (ROM x1) 6-2, 6-4
Jil Teichmann (SUI) bt Dalila Jakupovic (SLO) 6-3, 6-0
Vania King (USA) bt Natalia Vikhlyantseva (RUS) 7-6 (7/4), 6-3
Vera Lapko (BLR) bt Kateryna Bondarenko (UKR) 6-3, 6-3
Wang Qiang (CHN) bt Magdalena Rybarikova (SVK x31) 6-2, 6-2
Irina-Camelia Begu (ROM) bt Jennifer Brady (USA) 6-3, 6-3
Elina Svitolina (UKR x7) bt Sachia Vickery (USA) 6-3, 1-6, 6-1