Top-ranked Ash Barty assembled a major lead in her quarterfinal match at the Australian Open before her rival took an injury break and left the court.

Over an hour later, it was Barty taking suddenly off the exit. She was disturbed Wednesday by Karolina Muchova 1-6, 6-3, 6-2.

Cultivated No. 25, Muchova procured her first semifinal berth in a Grand Slam. Her rebound wins finished Barty’s offer to become the first Australian woman to win the title in Melbourne since Chris O’Neil in 1978.

“It’s heartbreaking, of course,” Barty said. “But the sun will come up tomorrow. You’re either winning or you’re learning, and today is a massive learning curve for me.”

Muchova’s adversary Thursday will be Jennifer Brady, who defeated individual American and good friend Jessica Pegula 4-6, 6-2, 6-1. Brady contacted her second sequential Grand Slam semifinal.

“I hope I make it a habit,” she said. “Hopefully I have a new habit of making finals.”

Seeded 22nd, Brady battled at times and gave her racket an angry toss midway during that second set. The unseeded Pegula, who advanced beyond the third round at a sign for the first time, seemed to tire down the stretch.

“We’re such good friends,” Brady said. “I’m really happy for her success. I know we’ll be having a lot more tough battles.”

Muchova played ineffectively toward the beginning of her second significant quarterfinal, and Barty raced to a 5-0 lead while losing just six points. After nine games, Muchova had one champ and 18 unforced errors, and early in the second set, she took an injury timeout that endured almost 10 minutes.

“I started feeling a bit lost,” Muchova said. “Ash started very well. She played almost like no mistakes; it was very tough. I was a bit lost on the court and my head was spinning, so I took a break. And it helped me.”

Medical personnel took her temperature, checked her blood pressure, and gave her ice before she left the court. At the point when the Czech returned, she played much better.

“I tried to play a bit faster rallies so we don’t play long ones as in the first set,” Muchova said, “and it worked well.”

Barty had no complaints to say about Muchova’s explanation behind the ending of the play.

“It’s within the rules,” Barty said. “She’s within her rights to take that time. That shouldn’t be a massive turning point in the match. I’m disappointed I let that be a turning point.”

Rebounds have been a staple in the competition for Muchova, who revitalized in prior matches to win sets in the wake of following 5-0 and 4-0.

Against Barty, she started moving into the court to hit her groundstrokes before. Barty, pushed behind the baseline, got uncertain and erratic.

During one stretch, Muchova won eight of nine games. Barty got done with 37 unforced mistakes and lost serve four times in the last two sets.

“I just overplayed,” Barty said. “I just pressed a little bit too much and gave up too many cheap errors at some pretty critical times.”

Muchova’s just other triumphs over a best five rival were against No. 3 Karolina Pliskova at Wimbledon in 2019.

Brady was in a two-week lockdown before the Australian Open since she was among the players who shared a contract trip to Australia with somebody who later tested positive for COVID-19.

The previous UCLA star contacted her first significant semifinal at the US Open in September before losing to inevitable champion Naomi Osaka.