To Toronto
Johny Gaudreau (retained @50%) this year and next...
To Calgary
Nick Robertson
Topi Niemela
2021 1st round pick
2022 2nd round pick
Thinking something like...
Nylander-Matthews-Marner
Gaudreau-Tavares-Hyman
Doesn't get you the center Calgary might want, but you don't take any money back, you get two excellent prospects and two quality picks and you clear 3.4 million in cap space this year and 3.4 million more at the end of next year.
In exchange, the Leafs take 2 quality cracks at the Cup, before choosing between Gaudreau and Nylander moving forward.