Dominik said the 26-year-old Jackson failed a physical. Jackson has been recovering from a shoulder injury.
Jackson had been with the Buccaneers since 2007, but he's had a troubled career. He was suspended for violating the league's substance-abuse policy two games into the 2010 season and returned for the final 10 games last year.
Dominik emphasized that he was not aware of any failed drug tests or disciplinary action coming down from the league.
"What's important to us as an organization is the growth of our football players," Dominik said. "And how they handle on and off the field to become the best Buccaneer possible. That's what we're looking for."
Jackson started every game he ever played for the Buccaneers and has 10 career interceptions.