MELBOURNE, Australia -- Jessica Pegula's first victory over a top-10 opponent earned the 26-year-old American her first trip to the quarterfinals of a Grand Slam tournament.

The 61st-ranked Pegula, whose parents own Buffalo's NFL and NHL franchises, held on to beat No. 5 seed Elina Svitolina of Ukraine 6-4, 3-6, 6-3 in Rod Laver Arena on Monday (Sunday night ET).

She will face No. 22 Jennifer Brady in an all-American quarterfinal.

Pegula is on quite a breakthrough run. She has won four matches at Melbourne Park over the past week -- including victories over two-time Australian Open champion Victoria Azarenka and 2011 US Open champion Samantha Stosur -- after entering the hard-court tournament with a total of three wins at majors for her career.

Also significant for Pegula, who works with Venus Williams' former coach, David Witt: She came into the day with an 0-6 record against top-10 women.

With the sky blue and the temperature in the low 70s Fahrenheit (low 20s Celsius), and zero fans in the stands for the third day in a row because of a local COVID-19 lockdown, Pegula dictated groundstroke exchanges from right along the baseline.

In the early going, she pushed around two-time Grand Slam semifinalist Svitolina, who eliminated American teenager Coco Gauff in the second round, and went up by a set and a break at 1-0 in the second.

Up until then, Pegula had not been broken.

But that's where Svitolina, with everything slipping away, made a stand. She suddenly broke Pegula twice in a row, part of a four-game run that put Svitolina ahead 4-1 in the second on the way to forcing a third set.

As if flipping a switch, or remembering what worked so well earlier, Pegula returned to her more aggressive brand of hit-to-the-corners play and led 4-1. She did get broken to 4-3 but broke right back, then served out the most important victory of her career by grabbing the last four points after falling behind love-30.

Brady made it to the round of eight at Melbourne Park for the first time by defeating No. 28 Donna Vekic of Croatia 6-1, 7-5 with the help of nine aces.

Brady went through two weeks of hard quarantine when she got to Australia last month because someone on her flight tested positive for COVID-19 upon arrival. She was not allowed to leave her hotel room at all during that time.

Brady is from Pennsylvania and played college tennis at UCLA. She was a semifinalist at last year's U.S. Open.

Vekic's right knee was heavily taped by a trainer early in the second set, but she kept things close from there until 5-all. That's when a double-fault handed over a break at love to Brady, who then served out the victory.

The last two women's fourth-round matches are No. 1 Ash Barty vs. unseeded American Shelby Rogers, and No. 18 Elise Mertens vs. Karolina Muchova.

The Associated Press contributed to this report.