If currentl assistant coaches all 3 of them have multi year deals left on their contracts and Savard leaves,talking about Smith,Delmore and Leighton I doubt Windsor will want to have them on the books, and 2 of Mitchell 's coaches are 23 and 29 years old,too young in my view for OHL,while Leighton's latest goalie pupil Costanzo finished in the top 5 in both goals against and save percentage for the regular season and the youngest in the league to register his numbers.
I would be surprised if any of the coaches moved on unless they wished too.
As for defense they won last year's conference championship with solid goaltending from both Medina 2.01 and Onuska 2.77 as well as solid d and offense.
My view defense is a team game not just the D.