With Chuck Pagano reportedly leaving the Bears for retirement, there are numerous possible replacements around the league to consider and some already in place on the staff.
Perhaps more importantly this could be the opportunity for the Bears to alter their scheme drastically and go to a 4-3 base instead of a 3-4.
The Bears had become synonymous with a 4-3 scheme since Bill George invented it in 1953 by stepping back off the line and assuming a middle linebacker position.. Then Dick Butkus cemented the position as a Bears legacy and Mike Singletary and Brian Urlacher followed the tradition.
The Bears have played the 3-4 since the start of 2015 when Vic Fangio was hired as defensive coordinator under John Fox.
While general manager Ryan Pace has built the right type of roster to fit a 3-4 scheme, there are strong personnel links to a 4-3 conversion.
The greatest reason for switching is the situation at edge rusher. Khalil Mack turns 30 next month and Robert Quinn already is 30. Playing a stand-up position with pass coverage responsibilities on some plays doesn't fit either as well now as it might have two or three years ago.
As a defensive end with a hand down in the 4-3, they could be in better position to rush hard off the ege without all the lateral movement and pass coverage responsibilities required of a 3-4 outside linebacker.
More importantly both had their best seasons playing with a hand down in the 4-3.
Quinn's entire career was spent as an end in a 4-3 with his hand down except for an 8 1/2-sack season in Los Angeles in 2017 and this past season with just two sacks for the Bears. Mack played end in the 4-3 from 2015-2017 with Oakland and had 15, 11 and 10 1/2 sacks. With the Bears as a 3-4 edge he's had 12 1/2, 8 1/2 and nine sacks.
In addition, 2020 fifth-round pick Trevis Gipson was brought in to be an edge but his natural position from college was playing end with his hand down and not standing up at linebacker. He could find it easier to make an impact.
The 4-3 requires a 3-technique defensive lineman who penetrates the gap between tackle and guard but the Bears' scheme uses 3-technique even though it's a 3-4 at times. Bilal Nichols is an ideal possibility at this position. Eddie Goldman is a nose in a 3-4 but has the versatility to be a 4-3 nose or defensive tackle.
Akiem Hicks might be a better fit for a 4-3 now at this point in his career. He could be a 4-3 nose and look for gap penetration or push back the center. He could be the 4-3 two-gap plug like Ted Washington was with the Bears when they used a 4-3 in 2001 and had the tackles holding up blockers rather than penetrating gaps like the Bears did in Lovie Smith's.4-3.
What the conversion will require is signing more off-ball linebackers. Danny Trevathan could be a middle linebacker but Roquan Smith is more suited to the position, and Trevathan most likely would be a player who is phased out. Smith is young and athletic enough to be an off-ball linebacker.
Coach Matt Nagy has never expressed a preference for one particular style defense over the other. He's been more involved with offense.
However, when he was with Kansas City the Chiefs always were in a 3-4 under former defensive coordinator Bob Sutton. With the Bears, it's always been 3-4, as well.
It's something the Bears should consider with their edge rushers approaching a certain age now but other athletic players like Roquan Smith still very young and capable of playing within either scheme.