'Invincible' Gauff revels in Melbourne heat to reach quarters
The American world number three beat Switzerland's Belinda Bencic 5-7, 6-2, 6-1 on a red-hot Rod Laver Arena to set up a meeting with 11th seed Paula Badosa of Spain.
"Two out of three sets at this stage of my career is not that physically hard for me," said the 20-year-old Gauff, who is chasing a first Melbourne title.
"The off-season I just put in so much work physically so I'm not worried at all about recovering emotionally or mentally," added Gauff, who won all five of her singles in Perth and Sydney to lead the US to a United Cup team triumph.
"The United Cup was a little bit more exhausting because of the fact that I finished at 1:00 am one night, then had to fly across the country and play.
"That was more of the mental, emotional test.
"Honestly, I feel like after playing that whole United Cup, I felt pretty invincible."
Gauff added that 34 degrees Celsius (93 Fahrenheit) temperatures during her match on Sunday did not bother her.
"I guess weather-wise, I felt pretty confident in my physicality," she said after her ninth victory of the season and 13th straight going back to last year's WTA Tour Finals.
"Being from Florida, like it was hot, but Florida in September, August, is really disgusting," she added.
The fourth-round encounter went with serve in the early skirmishes but the big-hitting Bencic's ability to mix up her shots unsettled the American.
Gauff had not dropped a set in eight matches this season, but was put under the pump by Bencic who converted a second break point in the ninth game.
"I thought in the first set that she played great tennis and it was tough for me to be on the offensive," said Gauff.
"I just played more aggressively in the second set and then also the third set. Overall, I'm happy with how I played."
Gauff turned it around in the second set to take it to a decider.
Tokyo Olympic gold medallist Bencic came in with a 2-1 win-loss record over Gauff but their last meeting was in 2023.
A few weeks later Bencic took maternity leave to give birth to daughter Bella and she only returned to tennis at the end of 2024.
A hard-fought hold after three deuces set the American on her way at the start of the third set as Bencic started to feel the heat.
Gauff wore her down and broke for 3-1 before closing out Bencic in 2hr 26min.
Badosa, who beat Serbia's Olga Danilovic 6-1, 7-6 (7/2), is into a quarter-final at Melbourne Park for the first time.