Coco Gauff tearfully bowed out at the hands of defending champion Naomi Osaka.
Meanwhile, Rafael Nadal won in straight sets and set up a meeting with 2014 champ Marin Cilic.
Here, we take a look back at day six, and forward to day seven, at the US Open.
Shot of the Day
The doubles is in full swing, and so was Jamie Murray with this over-the-shoulder number.
Stat of the Day
New York local Kristie Ahn, 27, is enjoying her home slam.
Osaka Consoles Gauff
Osaka beat friend Gauff 6-3, 6-0 and then consoled the 15-year-old afterwards.
Shock of the Day
Seventh seed Kiki Bertens was dumped out in straight sets by Julia Goerges, who is seeded 26th.
Johanna Konta could put her feet up and prepare for her fourth-round clash with Karolina Pliskova. The British number one is second up on Louis Armstrong. Dan Evans and Cameron Norrie lost in the doubles, but Jamie Murray and Neal Skupski reached the third round with a straight-sets victory over Ricardas Berankis and Juan Ignacio Londero.
Men: John Isner (14), Nick Kyrgios (28)
Women: Kiki Bertens (7), Caroline Wozniacki (19), Anett Kontaveit (21)
Arthur Ashe Stadium:
Roger Federer v David Goffin
Serena Williams v Petra Martic
Elina Svitolina v Madison Keys
Novak Djokovic v Stan Wawrinka
Louis Armstrong Stadium:
Qiang Wang v Ashleigh Barty
Johanna Konta v Karolina Pliskova
Dominik Koepfer v Daniil Medvedev