Filling the void of Fangio, a critical addition to first-year coach Matt Nagy's new staff a year ago, will be difficult for the Bears. Fangio inherited a Chicago defense ranked 31st in scoring in 2014 (27.6 points per game) and led it to first in the league in 2018 (17.7).
The Bears have a defense stacked with talent, with four Pro Bowl players, three of whom were also named All-Pros. The unit is built for 3-4 personnel, which could play into the hiring.
So who will be the Bears' next defensive coordinator? There are some intriguing possibilities in play.
Nagy would have to act fast in lining up his longtime friend Bowles for the role of Bears defensive coordinator. Bowles has agreed to become the Buccaneers' new defensive coordinator under new coach Bruce Arians but hasn't yet signed a contract, according to reports.
Fired by the Jets after four seasons as head coach, Bowles has a friendship with Nagy that dates back to Bowles' high school days, when Nagy's father coached him.
"I have so much respect for him," Nagy said of Bowles in October. "What he does defensively, but on top of that, too, I think he’s such a great human being. He does things the right way. He treats people the right way. I like how he does things."
Should Nagy and the Bears prioritize continuity for the defense, the obvious candidate is Donatell, who has served as the team's defensive backs coach for four seasons. A defensive coordinator in three prior stops and an NFL assistant of 26 years, Donatell has worked on Fangio's staff since 2011 with stops in San Francisco and Chicago.
Donatell is a respected coach who has overseen the growth of safety Eddie Jackson and cornerback Kyle Fuller into All-Pro players and has been lauded for the way he prepares his secondary. The Bears led the NFL with 27 interceptions, 21 of which were secured by defensive backs.
Donatell is no longer under contract with the Bears, according to the Chicago Tribune, meaning he's free to leave for a job elsewhere if he desires.
Just minutes after Fangio was tabbed as the Broncos' head coach Wednesday, a candidate for the Bears emerged in Williams, the veteran defensive coordinator who won't be retained on Freddie Kitchens' new coaching staff in Cleveland.
A longtime NFL coach, Williams has been defensive coordinator for 18 seasons with six different teams. He has had head two head coaching stints, including leading the Browns to 5-3 mark during an interim stint this past season.
Fired by the Broncos after two losing seasons, Joseph is considered a candidate for several defensive coordinator jobs. Chicago and Denver could work a de facto trade in adding Joseph as Fangio's replacement after Fangio became Joseph's replacement.
Joseph's dismissal in Denver came in part because of problems at the position of quarterback. His Broncos defense allowed 23.8 points per game last season, which ranked 13th in the league.
An interesting option for the Bears would be promoting second-year outside linebackers coach Staley, who was a key piece in getting Khalil Mack acclimated to their defense this past September.
Staley had previously served as defensive coordinator at John Carroll University and is highly regarded inside Halas Hall, especially by his players. If anybody would be willing to look past a light resume, it would be Nagy, hired as head coach after only eight years in coaching.