Linebacker Jack Sanborn’s rise from undrafted free agent to key player on the Bears ’ defense for three seasons was one of the team’s best success stories under former coach Matt Eberflus. Sanborn will rejoin Eberflus after agreeing to a one-year deal with the Cowboys, a source said.

The Chicago Bears are evaluating all aspects of their defense as they prepare to undergo any Dennis Allen-led changes. One of the biggest differences in personnel will come in the middle of the field.