ever stop to consider that a big part of the reason he does end up knocked over a lot is precisely because of his willingness to play a "big boy game"? He doesn't need to. He has the skill and vision to avoid or minimize contact the way suzuki or caufied do, but he recognizes that with his frame he can put pressure on opponents physically...
and...
he's 20 and has a lanky frame. He needs to, and will, add muscle and better coordination as he fully matures physically. With his work ethic, there's no doubt of that. So, instead of nitpicking because he doesn't have the muscle/strength yet to fight through all of the contact he initiates (and attracts) without getting knocked on his arse a bit... another way to look at it would be to be thrilled that he's got the understanding of how he can bring that element to the table and the competitiveness and willingness to take his licks without backing down.
net positive, rather than negative.
(and if you watch the Vegas/Avs series tonight, take a look at how often Mackinnon ends up hitting the ice... here's a hint, it's not because of any issues with his strength, skating or balance