Perk is bit overrated as a one on one defender. He's a great help defender because he understands where he and all his teammates need to be on the floor, and knows the rotations as much as KG. To says he's one of the best defenders at his position is just kind of a farce because there's just not that many great players in the league at his position. As far as true centers go, you can pretty much count on 1 hand who they are, and he won't hold his man to single digit point and rebound games very often, if at all. He is not the second coming of Ben Wallace. Having a good game against Robin Lopez or Joel Pryzbylla or Ronnie Turiaf does not impress me at all. He has had good games against good centers, but it's obvious that he gets lots of help in instances like the Orlando game when Howard has a very productive first half, but is a non factor in the second half. Not because Perk is a immovable force, but because Doc steps up the perimeter defense. When you have guys like Rondo, Pierce and Ray bothering the ballhandler on the perimeter it really helps Perk deny the ball. Perk can body up all day, but if you have one of those three, and even KG who flashes out and "shows" a lot, it's really hard for whoever has the ball to even get a pass into the post. The help defense isn't just in the post, it starts on the perimeter. As far as Perk goes, we will see in a few weeks just how good of a one-on-one defender he is when he's playing outside of the Celtics defensive system. Serge Ibaka will help him, but is he KG? Perk is no Ben Wallace--another very limited offensive player who was a shut down center and won three or four defensive player of the year awards. Perk has 0, and there's a good chance he will never win one.
Green has the tools, the IQ, the youth and soon, the opportunity. But the jury is still out on whether he will be an elite defensive player on our team--that too we will find out in the coming weeks.