Serena was scheduled to face Bulgarian Tsvetana Pironkova.
Former US Open champion Svetlana Kuznetsova has joined a growing list of players who have decided not to play in this year's tournament due to concerns over the COVID-19 pandemic.
Serena Williams has defeated her compatriot in four straight matches since a defeat in the quarter-finals of the 2013 Australian Open.
Serena Williams, hoping to win a record-equalling 24th Grand Slam singles title, will start her campaign against fellow American Kristie Ahn.
India's Nagal draws world No 128 Bradley Klahn in opener.
Australian Nick Kyrgios blasted 15 aces to blow past Japan's Yoshihito Nishioka 6-2, 7-5 on Thursday and reach the quarter-finals at the Citi Open in Washington.
Serena Williams did not need the help of a fan-filled Arthur Ashe Stadium to provide a lift during her 7-5, 6-4 win over the 96th ranked Kristie Ahn.
Images from Monday's action at the French Open.
News of all that's transpired on and off the tennis courts.
Images from Day 2 of the 2020 US Open in New York
Defending champion Naomi Osaka of Japan was upset 7-5, 6-4 by Belinda Bencic in the fourth round at the US Open on Monday as the Swiss reached the quarter-finals for the second time.
Images from Day 1 of the Australian Open in Melbourne on Monday.
Images from Day 1 of the Wimbledon tennis championships in London, on Monday.
Frenchman Benoit lost his temper in the third game of the second set when top seed Tsitsipas halted the match to attend to a broken shoe lace.
A summary of the second day's play at the US Open.
Images from Day 3 of the 2020 US Open in New York, on Wednesday.
Summary of sports events and persons who made news on Tuesday