I think that the Leafs must have some sort of agreement in place with Kessel either that or a good scoop that he wants to play for the leafs.
At anytime now a rival team can offer Kessel an offer sheet and scoop the player if Boston decides to match.
Remember that Charelli can not trade Kessel for a year if he has to match. This would mean Charelli would have to demote or trade one of Ryder and another asset.
I don't see another team wanting Ryder at 4 million a season. I also don't see Charelli demoting a guy they signed last year under his watch.
The Owner of the Bruins is supposedly cheap so I don't see him eating 4 million in the minors.
Kessel does not have to sign an offer sheet from another team. This is the reason I think Burke is confident that he can trade for Kessel because it doesn't seem as if he is nervous of another team signing him away by offer sheet.