There is no 100% sure way to tell but here is what us as scouts use to try to determin this...
The players improvment through the year, are they getting better? or are they just staying the same the whole year where they are doing well but other players are catching up, if the others are catching up then you have to look at ok what is it about this player that is not causing him to improve...have to look at a number of factors:
1. Look at last year, was it his size or skating speed that caused him to do very well against lower level and now that he is in the bigger leagues he can not adjust.
2. The players work ethic off the ice, is he dedicated, a guy who is going to work hard at achiving what he wants is going to do a lot better than a guy who gets by just on talent.
3. Hockey Awareness is a big one, you can teach someone to skate well, or handle a puck well but they way they see the game and think it is totally different that is what a player should have to be successfull.
Those are just three there are SO MANY i use as a scout to determin...
comparison is im going to use:
Nathan MacKinnon and Michael Lyle
though Lyle and MacKinnon IMO both are about equal talent wise in skill, MacKinnon is dominating in Shattuck whole Lyle is dominating point wise in a league as Nova Scotia Major Midget League...all through the years MacKinnon and Lyle played on the same line in Hockey Nova Scotia teams and will be on the CWG team together, both are amazing talents and Lyle outscored MacKinnon in the recent Atlantic Challenge Cup in Moncton...but MacKinnon I would take in a heart beat over Lyle I would not even have to think and here is why:
Lyle:
Pros:
Amazing hands with the puck, excellent playmaking, sees the ice very well, excellent shooting ability, has the ability to get past any defense, size.
Cons:
Work Ethic, heart, consistancy, Lazy.
MacKinnon:
Pros:
Amazing skating, great hands, amazing shooting, great playmaking, strong and good two way, great work ethic on the ice, plays with heart, and gives you 100% everyshift and does what it takes to win.
Cons:
Does too much by himself sometimes, needs to slow the pace down sometimes to use his teammates.
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So because of his heart, determination and work ethic MacKinnon has a much high cealing talent wise than Lyle, because both are amazingly skilled most probably do not know of Lyle on this board...but both are amazing players, but consistancy comes with hard work and MacKinnon has that and his great work ethic causs him to train harder on the ice causing him to always improve. Lyle has the ability to get drafted 2nd to 3rd overall in the QMJHL draft, but because of his low cealing because he doesn't want to work on the ice he might see himself go in the 2nd to 3rd round.