At night, Emma Raducanu became only the third defending U.S. Open champion to lose in the first round, eliminated by Alizé Cornet 6-3, 6-3.
Swiatek made 33 unforced errors in the 1-hour, 33-minute contest at No.1 Court. Cornet made only seven.
Djokovic isn’t vaccinated against COVID-19, while the U.S. requires visitors to be vaccinated to enter the country.
Serena Williams conceded it isn't easy to come to terms with spending time away from her daughter to focus on tennis.
Mihaela Buzarnescu beat fourth-seeded Cornet 6-2, 6-4 and Varvara Lepchenko had a 6-0, 7-6 win over 2012 winner Barthel.