Glennon was signed to a three-year, $45 million contract by the Bears less than one year ago with the initial plans for him to be the team's starter. Chicago, however, elected to select fellow quarterback Mitchell Trubisky with the second overall pick of the 2017 NFL Draft.
"The writing is clearly on the wall that Glennon will not be playing in Chicago next season," ESPN's Jeff Dickerson said.
Trubisky completed 196 of 330 pass attempts for 2,193 yards, the most among rookie quarterbacks in franchise history. The 23-year-old also threw for seven touchdowns and seven interceptions in 12 games.
Glennon struggled in four starts with the Bears in 2017, throwing five interceptions and committing eight overall turnovers during the team's 1-3 stretch.
The 28-year-old Glennon has thrown for 4,933 yards with 34 touchdowns and 20 interceptions in 25 career games since being selected by the Tampa Bay Buccaneers in the third round of the 2013 NFL Draft.