All this post suggested was that Dubas may have his hand forced to trade assets that may just walk at the end of the season - or perhaps start next season with less than what is proposed here.
Not a comfortable position for any GM, Columbus was certainly hurt by this exact situation when Bob, the Breadman & Duchene all left town
Maybe this is the fantasy version of making the best of a bad situation, but Dubas has to be considering precisely these issues right now

Tow of the toughest guys are O'Reilly and Crosby. Crosby is one of the most skilled players in the world but when there is a battle he decides he will win it and there is no other option. Hes the modern day grinder. Matthews has the skill to be a very good defensive forward and hes shown a bit of that this season but he hasn't shown his full potential yet. If they get guys to buy into playing like ilya mikheyev or zach hyman they will be unstoppable. They dont all need to go into the same things that they do but if they just take on the mentality that they cant be beaten then they will go far. They have the skills to back check, prevent cross seam passes and tighten up defensively without loosing their offensive flare but they dont. I dont care if they hit or fight that much but if they use their sticks to win battles and every time they lose the puck they do everything in their power to retrieve it, just like hyman would do.

On a separate note I dont think there defense needs that much of an upgrade. If they were able to learn how to effectivly stop the cycle and quickly turn the play in the other direction they wont need to make a big upgrade on defense until the summer.

Sorry that is absolutely untrue about playoff teams or even playoff teams worried about UFAs at the end of the season.. Gee if you haven't noticed those playoff teams actually trade for and give up good futures just to acquire those upcoming UFAs to make the their teams stronger through March to hopefully June.

No way is Dubas and other GMs in his situation thinking much about next. It's how to get my club stronger for this year. All teams have upcoming UFAs.. Leafs aren't unique.
Right now the Leafs have six Dmen pencilled in for next year. Plus they will have cap to make moves for an additional one or two Dmen next summer or even trade some cap forwards for a cap Dman(s).

having played D...if you give up 50+ pounds and one foot of reach to the people hitting, then forechecking you it is not a matter of what you "learn to"
Some players on the ice (namely your D partner) must possess the attributes (and yes skills) to overcome this.
Unfortunately size is the answer - exactly half the time in a D pairing
and a little mean streak is useful - occasionally