The defensive back missed the 2018 season because of a torn anterior cruciate ligament suffered in August.
He spent four seasons with Philadelphia, mostly as a backup and special-teams player, before signing with the Chargers last spring.
Watkins had a strong training camp and was carving out a spot to contribute before being injured.
“He was kind of going to be a nickel corner, a little bit of a safety,” general manager Tom Telesco said after the season. “We didn’t have him on the field long enough to see exactly what his role was going to be.”
The Eagles made Watkins the first selection in the fourth round of the 2014 draft. He has appeared in 36 career games and made five starts.