That's good in a way...
We need to get more scapegoats in training for the future.
(Just kidding)
It seems to me that Miller is playing a bit careful. On the 5 on 3 GA he should have stayed on his feet and kept his stick in the lane -- retaining some ability to react. But instead he kinda pulled a Staal. Went down, put his stick flat on the ice. which took him out of every play but one. The problem is, on a 5-3, there was literally no one else to pressure the passer, which meant he had plenty of time to tee up and try that saucer pass.
Again, I think Key was trying too hard to stay in his position. Same thing happened on the screen shot where he was in between two opponents in front of the net. He sorta took the man in front of him, but didn't move him out of the way. So, essentially, there were not 1 but 3 players screening Knight -- and that was in addition to the USA forward who also screened the release of the shot. Again, Miller was a bit too passive. He needs to use his size to push the opponent out and his frame to keep them out.
To me, it seems like a player who's afraid of running around and getting caught out of position. Once he feels more comfortable, I think he'll be more aggressive. After all, he shows his aggressiveness in other areas of the game, so I think it's just a matter of time. Also have to think that ref situation at the WJC where they're calling super soft penalties may be keeping him from making the more physically aggressive play. That said, from the little I've seen of him at Wisconsin this season, he's making similar adjustments.
Finally, it seems to be that Miller is still learning an early building block of D. Just knowing where he needs to be in all situations and then how to position his frame/stick to be the most effective. The good news is, he's rarely caught far out of position. So, he's generally in the right area. He just needs to refine what he's doing in those areas to defend better.