Keys, the tournament's fourth seed, received a first-round bye.
Navarro converted five of her seven break-point opportunities, while Keys broke serve three times on five chances.
Navarro advances to face former U.S. Open finalist Leylah Fernandez of Canada, who knocked out 13th-seeded Elise Mertens of Belgium 6-3, 6-4.
1 Ons Jabeur of Tunisia routed the United States' Alycia Parks 6-2, 6-2, and No.
The United States' Sofia Kenin eliminated 12th-seeded Anhelina Kalinina of Ukraine 6-2, 7-6 (5).
Persons:
Madison Keys, Aryna Sabalenka, Mike Segar, Keys, Navarro, Leylah Fernandez, Elise Mertens, Maria Sakkari, Australia's Storm Hunter, Caroline Garcia of France, Ekaterina Alexandrova, Poland's Magdalena Frech, Sofia Kenin, Lucia Bronzetti, Yi Yang, Bronzetti, Yang's, Uchijima, France's, Tatjana Maria of, Alexandra Eala, Daria Saville of, Germany's Anna, Lena Friedsam, Viktoria Hruncakova, Russian Anna Kalinskaya, Viktorija, Yulia Putintseva, Xiyu Wang, Yue Yuan, Zhuoxuan Bai
Organizations:
Madison, Belarus, Aryna Sabalenka REUTERS, U.S, Australia's Storm, Poland's, United, Thomson
Locations:
Flushing Meadows , New York, United States, Guadalajara, Mexico, Open Akron, U.S, Canada, Belgium, Tunisia, Greece, Belarus, Russia, Ukraine, Guangzhou, Italy, Taiwan, China, Tatjana Maria of Germany, Philippines, Daria Saville of Australia, Slovakia, Russian, Switzerland, Kazakhstan