According to Briggs today, it will not be a drastic change from Pagano's D. Desai is a product of Vic Fangio who does not blitz much. Briggs says "With the kind of money the Bears have invested in Khalil Mack and Robert Quinn — and Akiem Hicks for that matter — they shouldn’t have to dial up an abundance of blitzes to create routine pressure."
LINK "I think the Bears are in store for some subtle shifts, nothing drastic. There wasn’t a ton of difference from what Vic Fangio did to what Pagano did. In the history of defensive coordinator changes, my experience is the masses always clamor for the next guy to be more aggressive than the previous one. Blitz more. Pressure more. Attack, attack, attack. Well, no one takes over that position and states a goal of being more passive than the previous guy and operating with a bend-don’t-break approach. Desai was groomed by Fangio, who isn’t a big blitz guy. Fangio picks his spots to bring pressure, and the Bears were never among the league leaders in rushing five or more defenders when he was in charge. With the kind of money the Bears have invested in Khalil Mack and Robert Quinn — and Akiem Hicks for that matter — they shouldn’t have to dial up an abundance of blitzes to create routine pressure. The Bears used plenty of stunts and games up front last season, and I am sure we will see those again."
Desai has two main expectations from my point of view:
1) The pass rush was terrible last year and not much better in 2019 either. Bears have lots of $$$ invested in Hicks, Quinn, Mack, etc and need more consistent pressure out of their base rush package (i.e., without having to blitz excessively).
2) He has to get Eddie Jackson back to the ball-hawking centerfielder role he did so well under Fangio. The guy can't tackle for shit at/near the LOS anyway and the secondary is gonna need extra help in coverage this season w/o Fuller being there to lock down his man.
The above 2 factors (plus age) are the biggest reasons the defense went from one of the leagues best under Fangio to just so-so under Pagano.