Top seed Ashleigh Barty insisted nerves did not get the better of her as she let slip a 5-2 lead in the third set to bow out of the US Open after a shock third round loss to Shelby Rogers on Saturday.
World number 43 Rogers stunned the 2021 Wimbledon champion 6-2 1-6 7-6 (7-5) in a seesawing contest that lasted two hours and eight minutes.
Barty had a double-break lead in the third set and served for the match, before Rogers stormed back to win the next four games and triumph in a tie-break in front of a raucous Arthur Ashe Stadium crowd who cheered home the American.
It was the fourth time in the tournament that Barty had been broken serving for the match.
"No, I felt comfortable on the court," Barty told reporters when asked if there was an element of nerves. "I think that tension is natural. But I felt fine.
"I just didn't quite have enough physically or mentally in the tank but that's okay.
"We've had a great year so far. We're looking forward to celebrating the good stuff that we've done, learning from the hurt, learning from the experiences, and moving on."
Barty's third round exit adds to her ordinary record at Flushing Meadows, having never progressed further than the fourth round.
The Australian, who was absent from the US Open in 2020, was beaten by China's Wang Qiang in the 2019 fourth round as second seed, and went down to Karolina Pliskova at the same stage in 2018.
Barty would not be drawn on her record at Flushing Meadows, instead preferring to focus on her strong year, having been on the road for the past six months.
"The last six months have been a roller coaster," she said. "I think back to the very first match that I played on this trip. I was 5-2 down in the third set in the first round of Miami. Tennis has a funny way of evening things out, doesn't it?
"You can't win every single tennis match that you play. I'm proud of myself and my team for all the efforts we've put in in the last six months. It's been pretty incredible. I don't think we could have asked for much more honestly. I wouldn't change a thing.
"With all of the tough moments that we have had, it's created some of the most enjoyable experiences. I've learnt so much about myself, about them, the way that we work together. It's been truly an incredible six months."
Rogers becomes the first American woman to defeat the world number one in the first week of a major tournament since 1994, when Steffi Graf was shocked by Lori McNeil.
"I'm not sure I can," Rogers said on-court when asked how to describe the comeback from 5-2 down. "I tried to fight for every point. I didn’t want to leave, I said 'make balls, try to stay in this match'."
Rogers will face impressive British qualifier Emma Raducanu in the fourth round, while Barty confirmed she will now take a break but play at next month's Indian Wells.