Tributes from the sporting fraternity and the world at large poured in for Serena, who announced last month that she was "evolving away from tennis".
"Clearly I'm still capable," Williams told reporters. "But it takes a lot more than that. "I'm ready to be a mom, explore a different version of Serena.
"Technically in the world I'm still super young, so I want to have a little bit of a life while I'm still walking. I have such a bright future ahead of me."
Reigning champion Daniil Medvedev (26) set up a blockbuster fourth round clash with Nick Kyrgios (27) after beating Chinese qualifier Wu Yibing 6-4 6-2 6-2.
Italian Matteo Berrettini (26) squandered a number of chances in the third set but held his nerve to beat Britain's Andy Murray (35) 6-4 6-4 6-7(1) 6-3 to book a clash with Spaniard Alejandro Davidovich-Fokina.
Earlier, Coco Gauff (18) dominated fellow American Madison Keys to seal a 6-2 6-3 win to reach the fourth round at Flushing Meadows for the first time in her career.
Joining her in the next round was Tunisian fifth seed Ons Jabeur (28) who came through a thrilling clash against home favourite Shelby Rogers to win 4-6 6-4 6-3.
GARCIA CRUISES PAST ANDREESCU
France's Caroline Garcia continued her impressive run of recent results with a dominant 6-3 6-2 win over former champion Bianca Andreescu and set up a last-16 clash against Alison Riske-Amritraj.
CARRENO BUSTA TOPPLES DE MINAUR
Spaniard Pablo Carreno Busta, a two-times semi-finalist in New York, punched his ticket to the fourth round with a 6-1 6-1 3-6 7-6(5) win over Australian Alex de Minaur.
The 12th seed, who sealed victory with a tweener lob, takes on Karen Khachanov next.
RUUD OVERCOMES PAUL IN MARATHON CONTEST
Roland Garros finalist Casper Ruud dug deep to oust American Tommy Paul 7-6(3) 6-7(5) 7-6(2) 5-7 6-0 in a match that lasted four hours 23 minutes.
Up next for the Norwegian fifth seed is Frenchman Corentin Moutet, who became the first lucky loser to reach the second week at the US Open following his win over Pedro Cachin.
