I would love to see all areas of our team 'bolstered'. The playoffs are a long grind, and this season has already demanded more of the players than usual. Depth will be key.
That said, and with all respect to the suggestions already made, I wonder how much 'fit' enters into the conversation, and by that I mean the player(s) who are acquired before the TDL and their personal mindsets. It's been a long time since I've seen a Leaf team that appears to be as close as this one. For all the grief they take, at times, Thornton and Simmonds, name your favorite, seem to have balanced the room dynamic and there's a collective buy in from the players. That is a dynamic I want to strengthen, not lose. Example: I don't think Galchenyuk 4 years ago would be the player for the Leafs he is today. The guy is playing hard! He sees the opportunity, he is supported by the team, he ups his compete, and the results are encouraging.
I have no idea who Gally's comparables are, but I want those players who are excited to join the possibility, the strong possibility, of winning a Cup.
If so-and-so has to be cajoled into making the sacrifice of a week of isolation vs the guy who is all in, give me the latter...that guy is playing for the Cup. I want players who recognize the special opportunity that comes with joining this team, the career defining joy of winning it all, and for them that is the ultimate goal. They'll break down walls. It may be a Hall, or a far less recognized player, but whoever it is, I want that/those players who are 'all in'. They'll fit in with the culture that I believe this team is cultivating and add a dimension that helps the cause.
Palmeiri's hesitancy doesn't appeal (if this is true). Others the same. I want the guys who are willing to go all out for themselves and a team that gives them the chance to be champions.
