He's just not ready yet.
That's where we differ. I think he looks like a young defenseman who has had some slip-ups. I saw a lot of games played by Zach Bogosian on an internet feed when he was young and I'll tell ya, he was slow-footed and was walked all the time. Now he's pretty much the top-guy in Atlanta.
But in case you are right, let's relive another defenseman we all know that "wasn't ready."
This kid came into the league after being drafted very high, but the Hartford Whalers were not expecting him to make the lineup right away; the kid seemed to have anger issues and did not answer well to authority. They brought him in the next season anyway, due to a weak defense. He played his first season brilliantly for a young defenseman; 30 points and only a -3. But he still faced troubles and was traded, due to bar fights and so on. He comes to St. Louis and is hated instantly; fans are booing him. Head Coach Mike Keenan even asks him, "Do you know what I traded for you?" and benches him. The kid picks himself up, earns captaincy a few short seasons later and is now pretty much a slam dunk HOFer.
My point being, Pronger was not supposed to make the jump to the NHL instantly. But he was put in two different rough situations, persevered and has become a great player, partly because of it.
I would be willing to say that Pietrangelo could come through the same adversity and be a strong d-man. I'm not saying to throw him in against the top pairings in the league; let him play with Carlo and go about 14-15 min. a game. I'll state my point again from earlier; what purpose is Sydor or Brewer serving that Petro can't?