Before the 19/20 season, the CBA will likely be opted out if by one or both parties, creating a lockout. After the last lockout teams were rewarded 2 compliance buyouts, where they could get themselves out of any contract on the cap.
Is it possible there is a plan for Marleau to fall victim of this in his final year to fit the Leafs under? Same could be said for Horton if needed to deal with bonuses.