Said every GM in the league including his current one.
Therein lies the problem.
In fact even at his current price point there are only 11 players in the entire NHL that make more, and 3 are his teammates.
My suggestion to resolve this dilemma, is a sign and trade by Toronto first, that also forces them to retain $ and cap on the deal in order to make him palatable around the league in trade.
Leafs sign Marner to an 8 X $12.0 mil $96 mil deal and are forced to retain 25% (in order to find a taker) making him a 8 year @ $9 mil AAV player to his new team. Leafs have a 8 year X $3 mil dead cap space.
Now I know that sounds ugly from a Leafs POV, but the only other option which might be better is simply let him walk at seasons end and then use the $10.9 mil free cap space.
Pick your poison. !!!