There is no way to know if there is any actual cap savings in the rest of the years without knowing what the Leafs were prepared to pay from the beginning.
Suppose the Leafs were willing to pay 6 years at $7 million per year.
Doing the deal on Dec 1, the cap hit is still $7 million per year.
It is just in the first year that the $7 million is prorated for that whole year for a higher cap hit but that doesn`t mean the Leafs were willing to spend this prorated money from the beginning over the course of the contract.
Suppose the Leafs were willing to pay 6 years at $7 million per year.
Doing the deal on Dec 1, the cap hit is still $7 million per year.
It is just in the first year that the $7 million is prorated for that whole year for a higher cap hit but that doesn`t mean the Leafs were willing to spend this prorated money from the beginning over the course of the contract.