All depends on what is done this summer. Options are there but you need to get Marner signed, convince Marleau and the team of his choice to take him, and also try to find RD.
I think the biggest stumbling blocks are Marner and Marleau. Once you have Marner signed (who knows what the AAV will be) and Marleau traded to a team of his choice (Coyotes might be a good fit), that opens things up. If Marleau wants to stay, that creates a bigger problem in terms of who needs to be unloaded.
Zaitsev is under contract. If they can't move him, he has to play and he is a RD that the Leafs need. Problem is playing him in the top 4 when he is bottom pairing quality. At best he is a fringe top 4D quality but overpaid