I'm not sure you realize how hard it is to be as good as Alex Killorn at the NHL level. None of those guys are sure-bets. Erne's not going to step in and immediately produce as well as Killorn. You don't just "make room" for those guys. You make them earn their spots, and then, if you have to, you make room. Nobody's even come close to taking Killorn's spot yet.
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You just don't "Make room" for players who have not only establish experience in the NHL but who also have a track record of success. These new and upcoming players are not guranteed to perform in the NHL.