The NFL does not have a minor league system, so the closest thing a team has to a developmental system is its practice squad.
Players who are not good enough to stick on the 53-man roster but are too good to just let go typically land on a team's practice squad. Those players who land on that reserve unit are then given the opportunity to develop under the guidance of the team's coaching staff.
The NFL allows each team to keep eight players on the practice squad throughout the season, and there are a handful of players currently on the Chicago Bears roster who would benefit from a stint on the team's practice squad.