The payoff was a spot in the Australian Open semifinals against Danielle Collins, as Iga Swiatek took three hours in the afternoon heat to beat 36-year-old Kaia Kanepi.
The 20-year-old winner of the 2020 French Open said that the match was crazy. In the second set, I felt like she was playing so fast that I couldn't keep up. I had to finish my forehands.
The temperature hit 97 degrees on Day 10, continuing a week of hot days at the first Grand Slam tournament of the year.
Collins won the opening match on Rod Laver Arena before the heat got to her, and she was able to take a key service break in the final game of the opening set to win it.
Kanepi made her Grand Slam debut in 2006 but was playing in the quarterfinals in Australia for the first time, completing a career set after making it to the last eight twice at other major tournaments.
She was coming off an upset, three-set win over No. 2-ranked Aryna Sabalenka and took the game to Swiatek, who saved nine set points before losing the first set.
Swiatek won it in a tie after exchanging service breaks twice.
Swiatek was broken in the eighth game of the third set when she was serving for the match. She eventually won on Kanepi's serve, scrambling to stay in the point until Kanepi sent a forehand wide.
The first three quarterfinals were decided in straight sets, and the last one went all the way.
Swiatek wrote a thank you on the TV camera lens as she left the court.
There are two Americans in the last four. Barty, the French Open winner, will play Keys, the US Open runner-up.
Swiatek is the only one of the four who has never been to the Australian Open semifinals. Collins had her best run to date at a major when she lost to Petra Kvitova in the semifinals in Australia. Keys and Barty lost to Serena Williams in the same year.
Collins had surgery last year to treat a condition that caused her severe pain during tournaments.
Collins said in her post match interview that it feels incredible, especially after some of the health challenges she has had.
I feel good right now. I have had some great matches at this tournament and I am happy with how I am feeling.
The loss ended a career-best run for Cornet. She was in the quarterfinals for the first time. The women's tennis association thinks that the 32-year-old should return to the top 50.
The power in the ground strokes was more than what I expected, even though Cornet had anticipated an aggressive game strategy from Collins.
I felt out of breath all the time. She never gave me the time to play my game.
The report was contributed to by the Associated Press.