NEW YORK -- An upset Garbine Muguruza let Barbora Krejcikova know that she thought the eighth-seeded Czech was "unprofessional" by taking a medical timeout just as the ninth-seeded Spaniard had the momentum in the second set of their fourth-round match at the US Open.
Krejcikova beat Muguruza 6-3, 7-6 (4) in a match that didn't finish until after 1 a.m. ET Monday. There came some drama at the end as Krejcikova called for the medical timeout -- saying she wanted to see the trainer for a diaphragm issue -- after Muguruza had overcome a 4-0 deficit in the second set to take a 6-5 lead.
When play resumed after the break, Krejcikova won seven points in a row. She also angered Muguruza by taking her time between points down the stretch, slowly walking over to her towel.
When the two went to briefly shake hands at the net, a clearly annoyed Muguruza told the reigning French Open champion she thought her behavior was "so unprofessional."
When the match was done, Krejcikova stayed in her sideline chair, hunched over, until eventually leaving the court with some assistance. She did not do the postmatch winner's interview on the court.
"Listen, I don't really want to talk about this," Muguruza said when first asked about what happened late in the second set. "I'll let you guys judge what you think about this."
Told by a reporter that she seemed upset, the two-time major champion replied: "Well, I think, between players, you know a little bit how to behave in certain moments and, yeah, I wasn't very happy at the end of the match. That's pretty much it."
Krejcikova did not appear at a postmatch news conference. In comments distributed by the U.S. Tennis Association, Krejcikova said: "At the end, I was really struggling and I feel really bad right now. I don't really know what happened, but I couldn't breathe. I started to feel dizzy, and the whole world was shaking. It never happened to me before.''
Krejcikova is headed to the US Open quarterfinals in her singles debut at the hard-court Grand Slam tournament. She next plays second-seeded Aryna Sabalenka of Belarus.
The Associated Press contributed to this report.