Jessica Pegula said she "can't be more confident" after upsetting Elina Svitolina to reach her first grand slam quarter-final and Ash Barty stayed in the hunt for Australian Open glory on Monday.
Pegula, the daughter of NFL and NHL franchise owners of the Buffalo Bills and the Sabres, beat fifth seed Svitolina 6-3 3-6 6-3 on Rod Laver Arena to set up a showdown with her fellow American and friend Jennifer Brady.
Brady made it all the way to the semi-finals of the US Open last year and has now put together her best run at Melbourne Park after seeing off Donna Vekic 6-1 7-5.
World number one Barty has not dropped a set in her home major and started the second week by dispatching Shelby Rogers 6-3 6-4.
The top seed from Queensland's next assignment will be a meeting with Karolina Muchova, who saw the back of Elise Mertens 7-6 (7-5) 7-5.
Muchova, the 25th seed from the Czech Republic, has made it through to her second grand slam quarter-final - having also reached this stage at Wimbledon in 2019 - without losing a set.
Pegula to put friendship to one side
Pegula and Brady are close friends, but they will have to put that to one side when they meet in the quarter-finals.
The world number 61 claimed her first victory over an opponent ranked in the top 10 just over a month after Svitolina beat her in straight sets in Abu Dhabi.
Pegula hit 31 winners to Svitolina's 19 and won 21 points from 29 when she made a trip to the net as she broke new ground at a major
She said: "I can't get more confident, it's my best result yet and I'm playing good tennis. Today was a hard-fought win, so, yeah, feeling pretty good."
Pegula added on the prospect of facing Brady: "We're here to have fun and compete. If I can do it against somebody that I like, that I wouldn't mind if they beat me, hopefully not, but if they did, why not?"
Brady benefited from strict lockdown
Many players understandably struggled during and after being in a strict two-week lockdown in a hotel room following their arrival in Australia.
Brady was among the players who were not allowed out of their rooms for a fortnight, but said she used the situation to recharge her batteries before the first major of the year.
The 22nd-seeded Pennsylvanian said: "I think it was a little bit of a benefit for me, just taking a break from tennis. I had been going non-stop since World Team Tennis in June. I didn't take any time off.
"I was playing from June and then played US Open, the U.S. tournaments, and then went straight to Europe, then finished there and was training in Europe, then went home for Christmas and then came and started in Abu Dhabi.
"So obviously I didn't really feel super fresh mentally coming into Abu Dhabi. And then when I was away from tennis for two weeks, I felt like I wanted to play again to compete and I think that helped me."
Much improved Czech
Muchova had not been beyond the second round of the Australian Open before last week but now has a semi-final spot in her sights.
The 24-year-old was 4-0 down in the opening set as Mertens got off to a flyer but warmed to the task with her battling spirit and positive approach.
Muchova converted five of the six break points she earned on Margaret Court Arena, also coming from a mini-break down in a first-set tie-break.
She struck 25 winners to Mertens' 15 and advanced despite making 31 unforced errors, getting her rewards for throwing caution to the wind.