It could be any number of reasons, but he has shown incredible resiliency since his draft.. big guys take much longer to develop, like defenders. Unless they are franchise type(s) like matthews, mcdavid, etc...Something that we have to look at with him is his training last Summer.
Remember when he said in September that he wanted to loose some weight in the Summer and he was at 217 pounds...
Remember the summer of Kk after his first season...he cameback and he was awfull...always on his ass...apparently all he did that Summer was playing Tennis...
Slaf said that he tried someting New last Summer but never gave the details but it d'id't helped him at all.
As a fan , or journalist etc we don't really know exactly about their training and it is so important cause for Habs players ( when we don't make the playoffs) it is 5 months...and it is huge at that age..
Slaf is not as strong on his legs than the last 50 games.of last season.
I am tellijg you..his last Summer's training has something to do with it