The 2020 US Open is in full swing in Flushing Meadows, with the Round of 16 beginning on Sunday afternoon.

Sunday's action will feature some of the top stars in the sport, including men's world No. 1 Novak Djokovic and former US Open champion Naomi Osaka in the women's field.

But the day began with a notable upset, as American Jennifer Brady defeated three-time Grand Slam champion Angelique Kerber in straight sets (6-1, 6-4) to advance to the first Grand Slam quarterfinal of her career.

The women's field  at the US Open was something of a wild card this year, with world No. 1 Ashleigh Barty and world No. 2 Simona Halep both opting out due to health concerns regarding COVID-19. Last year's champion, Canadian Bianca Andreescu, also opted out.

Things became even more wide open when top-seeded Karolina Pliskova and No. 5-seeded Aryna Sabalenka both fell in the second round.

Kerber, meanwhile, came into Sunday's match against Brady without having dropped a single set. The German seemed poised to win the fourth Grand Slam of her career and her second US Open title.

But Brady had other things in mind. The 25-year-old hit 25 winners and won four of her 10 break points, whereas Kerber converted just one of her six break opportunities. Brady will now await the winner of Sunday's match between Petra Martic and Yulia Putintseva.

Serena Williams and Sofia Kenin are among the more notable Americans still remaining in the women's field, but Brady is making an inspired run of her own at the US Open after winning the Top Seed Open in Lexington last month.