US Open: Madison Keys overwhelms No. 3 seed Jessica Pegula to advance to quarterfinals

Madison Keys broke Jessica Pegula on her first serve Monday and didn't look back.

The 17th-seeded Keys dominated her fellow American 6-1, 6-3 to advance to the US Open quarterfinals and send the No. 3 seed home in an upset victory.

Keys won four straight points on serve to strike first in the game's opening set. Pegula then scored on her first serve in the second set but lost four consecutive points to drop a break and go down 2-0. Pegula held on her next serve to cut her deficit to 3-1. But she wouldn't win another game in the opening set.

Pegula then held to win the opening game of the second set. But Keys broke her third serve of the set to take a 3-2 lead.

Pegula returned the break to tie the set at 3-3. But she didn't win another game as Keys cruised to victory in 1:01.

The loss continues Pegula's late-stage woes at majors. The 29-year-old has won three career titles but never advanced past the quarterfinals in Grand Slam play.

Keys, meanwhile, returns to the quarterfinals at the site of her career-best Grand-Slam performance, a trip to the US Open final in 2017. There, she lost to fellow American Sloane Stephens in straight sets.

The loss is the second for a top-three player in the women's bracket in two days after No. 20 Jelena Ostapenko defeated No. 1 seed Iga Swiatek on Sunday. No. 5 seed Ons Jabeur also lost Monday, falling to No. 23 seed Qinwen Zheng, who advanced to her first Grand Slam quarterfinal with a 6-2, 6-4 win.

No. 2 seed Aryna Sabalenka advanced in straight sets Monday, with a 6-1, 6-3 victory over No. 13 seed Daria Kasatkina. She'll face Zheng in the quarterfinals. She has clinched the World No. 1 ranking next week regardless of the match's outcome because of Swiatek's loss.

Keys advances to face reigning Wimbledon champion Marketa Vondrousova (No. 9 seed) in quarterfinal action scheduled for Wednesday.

Pegula's US Open, meanwhile, isn't finished. She returned to the court just hours after her loss alongside Coco Gauff in doubles play against Marta Kostyuk and Elena-Gabriela Ruse, and they won 6-4, 6-1 to advance to the quarterfinals. Pegula is also competing in mixed doubles, where she has advanced to the quarterfinals alongside fellow American Austin Krajicek.