Madison Keys smashed No. 3 seed Jessica Pegula 6-1, 6-3 on Monday in New York to reach the quarterfinals of the U.S. Open for the first time since 2018.

Keys, the No. 17 seed, needed just 61 minutes to win the all-American affair. She converted five of nine break chances and finished with 21 winners to just six for Pegula.

"It's always tough having to play a friend," Keys said during her courtside interview. "... When we get on the court it's all business."

Keys was the runner-up to Sloane Stephens at Flushing Meadows in 2017 and a semifinalist in 2018.

"I've had so many amazing moments in New York," said Keys, who won 77 percent of her first-service points in a match that featured few long rallies.

She will next face No. 9 seed Marketa Vondrousova of the Czech Republic. The reigning Wimbledon champion rallied to beat unseeded American Peyton Stearns 6-7 (3), 6-3, 6-2 in the fourth round on Monday.

"She was playing great from the beginning, and I just tried to stay in the game," Vondrousova said. "I'm very happy. I actually didn't expect it after Wimby -- it was a lot of pressure. We'll see what happens next."

Vondrousova served nine aces and took advantage of 52 unforced errors by Stearns, including 21 in the final set, to reach her first U.S. Open quarterfinal.

No. 2 seed Aryna Sabalenka of Belarus is the highest seed left standing in the women's draw after Polish No. 1 seed Iga Swiatek lost on Sunday. Sabalenka cruised to the quarterfinals by beating Russian 13th seed Daria Kasatkina 6-1, 6-3.

Sabalenka started her season by winning the Australian Open for her first Grand Slam title. She reached the semifinals at both the French Open and Wimbledon, but not further.

"It's kind of similar to the Australian Open -- the courts, the balls, the conditions," Sabalenka said in her on-court interview. "I was very unbelievable here as well.

"I just don't want to say that it's even better here because I think my Australian fans will be a little bit... a little bit sad with that news," she added with a smile.

Sabalenka owned points at the net, winning 11 out of 15. She had a whopping 31-7 edge over Kasatkina in winners despite not hitting an ace.

Sabalenka's quarterfinal opponent will be 23rd seed Qinwen Zheng of China, who upset No. 5 seed Ons Jabeur of Tunisia 6-2, 6-4.

Zheng had 21 winners and 17 unforced errors, while Jabeur hit 17 winners and committed 33 unforced errors. It marks Zheng's first appearance in a Grand Slam quarterfinal.

--Field Level Media