I haven't seen enough of Staal, so its stupid for me to attempt to compare the two.
But people should realize that Barker is not a Coffey/Housely type of "offensive defenseman". He's much more of a Rob Blake/Nik Lidstrom *type*.
In fact, I think his game is more like Lidstrom's than any other NHL dman I can think of. Now I am in no way saying that he will be that good (odds are that he won't even be close)- but that is the type of game he plays.
He is big, but not physical- he is a positional dman.
He doesn't have the huge point shot. His shot is hard, accurate and has a knack getting it through.
He doesn't have high end speed or acceleration, and I haven't seen him take it end to end ala the great "offensive dmen". What I have seen him do is knock the puck down at the blueline- deke a rushing forward, and move into space getting the angle for a shot.
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Anyway, that is the type of dman Barker is, and will be. Its a double edged sword, really. When those types of dmen get to the highest level- they are like Blake or Lidstrom (top dmen in the league). When they don't, they are a disappointment because you expect them to do more.
I don't think anyone can honestly say how Barker will turn out at this point. He did look great against other prospects, but we'll see how he does against NHL'rs in training camp.
-fullmetalninja