Nagy, who the Bears named as the 16th head coach in franchise history on Monday, was hired to breathe new life into Chicago's dormant offense, which is tied for 30th in points since 2015.
Selecting Nagy over candidates such as Minnesota's Pat Shurmur or Philadelphia's John DeFilippo had nothing to do with the state of Chicago's defense.
The Bears are crossing their fingers that Vic Fangio's head-coaching interview last week appeased the decorated defensive coordinator enough to stick around and join Nagy's staff, but if not, the Bears will still run a version of the 3-4. The Bears have to address cornerback and outside linebacker in the draft/free agency, but they won't overhaul the defense. Fangio and his defensive assistants laid the groundwork for future success on that side of the ball.
Rather, Nagy's arrival is all about offense, and most importantly, Trubisky's development. The Bears are banking that Nagy's experience with Alex Smith in Kansas City -- and his very limited, but successful, playcalling stint under Andy Reid -- prepared him to devise a scheme that can maximize Trubisky's strengths.
For all of Bears general manager Ryan Pace's grandiose statements in regards to Trubisky's potential, the draft's second overall pick finished the season with seven touchdowns and seven interceptions over 12 starts for a 77.5 quarterback rating.
Those pedestrian numbers can partly be attributed to Trubisky's weak supporting cast, injuries, and Chicago's questionable playcalling, but even Trubisky's biggest supporters have to admit that the quarterback has ample room for improvement.
That's how Nagy will ultimately be judged.
Nagy's relationship with Reid is a nice bonus. Reid's coaching tree now includes six NFL head coaches, with Nagy joining Ron Rivera, Sean McDermott, John Harbaugh, Doug Pederson and Todd Bowles.
However, former Bears coach John Fox (14-34) at one time worked under Chuck Noll. Marc Trestman (13-19) coached in Oakland under Jon Gruden. Dave Wannstedt (40-56) coordinated Jimmy Johnson's defense. Dick Jauron (35-45) spent several seasons alongside Tom Coughlin in Jacksonville.
Without question, Nagy arrives in Chicago full of firsthand knowledge about what a successful offense is supposed to look like. The key will be applying those lessons learned from Reid here in Chicago, where the fan base is starved for a winner.
If Nagy has Trubisky playing at a high level in 2018; chances are everything else falls into place. The Bears can't be good next year unless the quarterback takes a major step.
Everyone knows that.
That's why it shouldn't take long to determine whether Nagy is the right man for the job.