BonkTastic
ಠ_ಠ
Well they're currently paying Ceci/Barrie a combined $7.25 million to be not great defensively while also being forced to play Holl/Gravel/Marincin in bottom pairing roles while their kids marinate. There's a world where they can actually improve defensively (mind you, while losing some offence on the back end) if they let Barrie/Ceci/Holl/Marincin/Gravel walk while replacing them with UFA (shutdown type)/Dermott (increased role)/Sandin/Liljgren.
It's not an easy task, but it's not out of the realm of possibilities either.
Part of Toronto's defensive issues as well is the fact that they traded away two of their strongest defensive forwards in C.Brown and Kadri.
Even if they add a guy on the back end, they still created defensive holes among the forwards and especially on the PK where Brown was basically the 1st unit shutdown guy on the wing. Kadri was, for all his other flaws, a physical two-way guy who played solid hockey at both ends.