NEW YORK (AP) Johanna Konta sat on a towel along the baseline, her racket resting by her feet, an ice bag under each arm, chest heaving.
Fans murmured with concern in the stands and her opponent stood next to her chair, unsure what to do.
Asked later how she was feeling - physically - the 25-year-old Brit replied instead: ''I'm feeling a little embarrassed.''
Konta had keeled over while trying to start her service motion, one point from losing the second set of her U.S. Open match. Down on the court for 7 1/2 minutes, she came back out to hit one serve into the net for a set-ending double-fault, after which she headed to the locker room to change her sweat-drenched outfit.
Then the 13th-seeded Konta returned to win the third set for a 6-2, 5-7, 6-2 second-round victory over Tsvetana Pironkova that lasted more than 2 1/2 hours.
With Konta serving at 5-6 in the second, the game dragged on for 10 minutes, including four deuces and four rallies of at least 10 strokes. After the last and longest of those - an 18-shot point - Konta missed her first serve, then bent over as she attempted the second.
She went down to her knees, gasping for breath. Her heart was racing, her body shaking.
Pironkova came to the net; the chair umpire rushed over. A ballperson laid a towel next to her, and the chair ump handed her several bags of ice.
Four minutes passed before medical staff got to Konta, who had rolled onto her back by then. They checked her pulse and her blood pressure, held a thermometer to her ear and a stethoscope to her back.
Pironkova sat in her chair, staring off blankly, legs bouncing.
Something like this also happened to her about four years ago on a hot and humid day at another tournament in the U.S., Konta said, though she couldn't remember the details.
''Because I'd experienced it once before, I didn't start crying,'' she said.
Focused on controlling her breathing, Konta put together an efficient third set to move on.
''I just played with what I had,'' she said.
''I feel quite certain that with some TLC I'll be good to go again in a few days' time,'' Konta added.
All the delays - the medical timeout, the toilet break - were within the rules, Pironkova agreed. That didn't make it any less maddening.
''What wasn't fair to me was what happened after that - the toilet break,'' she said. ''Because with that toilet break the match was stopped for just too long. ... Today I am not very happy about the rules.''
The 71st-ranked Bulgarian, a French Open quarterfinalist this year, had rallied from down a break in the second set.
''It was an unfortunate time,'' she said. ''I had my momentum going. I was getting back in the match. ... That break, somehow, maybe stopped that momentum.''
Konta didn't want to speculate about what exactly caused her issues Wednesday, when temperatures were in the mid-80s. She did note she's played a lot in recent weeks - 16 matches since the end of Wimbledon.
''It's hard to feel the difference between general tiredness, general fatigue, once you cross over to where your body starts shutting down a bit,'' Konta said. ''I think all athletes kind of play a very fine line with that. We push our bodies to the limits that they can go. I definitely hit, you know, one of my limits. That was the way my body reacted.''
A year ago, Konta needed to qualify to get into the U.S. Open. Then she advanced all the way to the round of 16 - the first time she'd been past the second round at a major. That was part of a 16-match winning streak against various levels of competition that sparked a surge up the rankings, and she went on to make the semifinals at the Australian Open.
Ninety-seventh in the world coming into the 2015 U.S. Open, Konta has her best career seeding at a Grand Slam at this year's tournament.
Asked why she found Wednesday's travails so embarrassing, Konta explained: ''I'm out there to play my sport, to showcase my sport. I'm not an actress. I'm not a drama queen.''