Feb. 17 (UPI) -- Karolina Muchova knocked No. 1 Ash Barty out of the Australian Open with a quarterfinals win on Wednesday in Melbourne. Jennifer Brady also advanced to the semifinals with a victory over fellow American Jessica Pegula.
"I'm happy that with each match I'm bringing my level up," Muchova told reporters.
Muchova's win over Barty means that just one Top 10 player -- Naomi Osaka -- remains on the women's singles circuit. Muchova -- ranked No. 27 -- trailed Barty in many statistical categories in Wednesday's win, but used a late rally to stun her Australian counterpart 1-6, 6-3, 6-2.
"It was a tough one today without a doubt," Barty told reporters. "I would have loved to have done a little bit better, but it wasn't my day today."
Muchova now will meet Brady in the semifinals on Friday in Melbourne.
Barty sizzled at the start of Wednesday's match. She won the first five games and appeared in control of the bout. Muchova then won the sixth game, but Barty finished out the set with a win in the seventh game.
Barty again won the first two games of the second set. Muchova then called a medical timeout, which prompted a break in play.
She was errant to start the match, but had a renewed focus when she returned. She went on to prevail in the next three games.
"I think it was the heat," Muchova said. "I was feeling really dizzy and almost fainting. I just asked for help."
Barty tied the third set with a win in the sixth game. Muchova then finished out the second set with three consecutive game victories.
Muchova continued to rally in the third set. She won six of seven games and then broke Barty's serve to take a 2-0 lead in the third set. She broke Barty's serve again to take a 5-2 lead and saved three break points to secure the victory.
Muchova won the final three games of the match. She claimed match point with a 99-mph ace.
Barty had three aces, three double faults, won three of 13 break points, had 21 winners and 37 unforced errors in the loss. Muchova had two aces, three double faults, won four of 11 break points, had 17 winners and 33 unforced errors in the one-hour, 57-minute match.
Brady edged Pegula 4-6, 6-2, 6-1 in a one-hour, 40-minute match on Wednesday.
Brady -- ranked No. 24 -- had seven aces, won seven of 10 break points and fired 22 winners in her win over the fellow American. Pegula -- ranked No. 61 -- did not have an ace, won four of 10 break points and had 15 winners in the loss.
No. 6 Stefanos Tsitsipas also scored an upset victory on Wednesday, with a hard-fought win over No. 2 Rafael Nadal on the men's singles circuit. Tsitsipas won the four-hour thriller 3-6, 2-6, 7-6(4), 6-4, 7-5 on Rod Laver Arena.
"I'm speechless," Tsitsipas said in an on-court interview. "I have no words to describe what happened. It is an unbelievable feeling to be able to fight and give it my all on the court.
"I started very nervous. I don't know what happened after the third set. I flied like a little bird."
Tsitsipas had 17 aces, zero double faults, won two of five break points and had 49 winners in the victory. Nadal had 15 aces, two double faults, won three of four break points and fired 58 winners in the loss.
Tsitsipas battles No. 4 Daniil Medvedev in a men's singles semifinal on Friday in Melbourne.
Medvedev on Wednesday advanced to the semifinals with a 7-5, 6-3, 6-2 win over No. 8 Andrey Rublev.
Medvedev had 14 aces, won five of 11 break points and had 30 winners in the two-hour, five-minute match. Rublev had eight aces, won one of five break points and fired 20 winners in the loss.
The winner of the Tsitsipas-Medvedev match faces No. 1 Novak Djokovic or Aslan Karatsev in the men's singles final of the 2021 Australian Open.
Djkovic and Karatsev face off in a men's semifinal at 3:30 a.m. EST on Thursday on ESPN.
No. 3 Naomi Osaka also faces No. 11 Serena Williams at 10 p.m. EST on Wednesday on ESPN for a trip to the women's singles semifinal. The winner of that match battles Brady or Muchova in the women's final.