WATCH the US Open from the quarter-finals onwards LIVE, FREE and in HD on SBS from 2am (AEST) Wednesday September 9 or live stream via SBS On Demand here.
The shock of the day was women's number one seed Karolina Pliskova getting knocked out in straight sets by Frenchwoman Caroline Garcia.
Garcia dominated the first set 6-1, and while Pliskova improved in the second she went down 7-6 (6-2) in the tiebreak.
Men's top seed Novak Djokovic had a wobble of his own, dropping the first set 7-6 (7-5) to Britain's Kyle Edmund, but he cruised through the next three sets winning them 6-3, 6-4, 6-2.
The only Aussie in action today was Jordan Thompson, who is through to the third round after defeating Belarussian Egor Gerasimov 6-1, 6-4, 3-6, 6-3.
2018 winner and women's fourth seed Naomi Osaka made light work of Italian Camila Giorgi, advancing 6-1, 6-2.
In other big matches, men's fifth seed Alexander Zverev downed American Brandon Nakashima in four sets, and 2016 winner Angelique Kerber knocked out fellow German Anna-Lena Friedsam in straight sets, and Greece's Stefanos Tsitsipas defeated American Maxime Cressy also in straight sets.