What's wrong with the Celtics Defense?

   Ever since Kevin Garnett stepped on the Parquet Floor the Boston Celtics have been know for their suffocating defense. They were a juggernaut that forced teams into unfamiliar situations. They hounded players on the perimeter and made them fear venturing into the paint with guys like Kendrick Perkins controlling the middle. Now they're a small team that is struggling guarding Pick & Rolls,Protecting the rim and 3 point shots which are all necessities to being a great defensive team. Right now the Celtics are 19th in Points Allowed per game(99.3), 27th in Opponents FG%(.463), and 23rd in Opponent 3pt FG%(.368) which are all team lows since the "Big Three" Era began in 2007-08.
   Right now it just seems as if the Celtics dont have the personnel to be a great defensive team. They don't have the size necessary to challenge opponents at the rim or near the basket. According to HoopData.com the Cetlics 5th worst defensive team at the rim with opponents shooting 67.7% and they're the 3rd worst defensive team at 3-9 feet with opponents shooting 45.9%. I think we all knew going in that this team was going to have trouble defending the rim since they primarily play very small lineups with Kevin Garnett being really the only legit 7 footer in the rotation. Now there is still some reason to have hope with defensive ace Avery Bradley scheduled to make his return sometime in mid December. Last year according to 82games.com 4 of the top 5 lineups which featured Avery Bradley gave up less than a point per possesion. Avery's defensive is so important to this teams success. His ability to pressure the ball in the backcourt and take precious seconds off of the shot clock is so invaluable to this team.
   Maybe this season's defensive struggles can attributed to the lack of chemistry between new guys or that it still is missing one of it's premier defenders, whatever it is it needs to be fixed. If this team is going to compete for a championship the defense needs to return to it's former glory.