Both players will have MRI tests on Monday. Bradley left the field on his own after getting hurt about halfway through the session. The extent of his injury wasn't immediately known, though trainers appeared concerned.
Bradley, a third-round pick in 2007, had 151 tackles in his first full season as a starter last year. He's the primary signal caller on a defense that already lost veteran safety Brian Dawkins in free agency.
Hobbs, acquired in a trade with New England, is competing for a starting job with Sheldon Brown.
A total of 31,786 fans came out to Lincoln Financial Field to watch the inaugural Eagles Flight Night. Proceeds from the event benefit the team's charities.