Freeman, 31, was suspended 10 games last season for a second violation of the league's policy on performance-enhancing substances.
The Bears placed Freeman on injured reserve in Week 2 after the veteran tore a pectoral muscle in the season opener versus Atlanta. Freeman suggested that the concussion he suffered in the Falcons game contributed to the latest suspension.
Freeman -- voted a team captain before Week 1 -- missed four games in 2016 for his first violation of the PED policy but still finished with a team-high 110 tackles.
He played four seasons in Indianapolis, registering at least 100 tackles three times, before he signed a three-year deal with Chicago in 2016.
Freeman was scheduled to earn $3.5 million in 2018, but none of it was guaranteed.
ESPN's Jeff Dickerson contributed to this report.