Duncan.
At his absolute peak, he posted the 6th best defensive rating of all time. Among active NBA players, he's #1. For career defensive rating, he's #3. Second in active win shares (behind only Kevin Garnett), Third in active win shares per 48 (behind Chris Paul and LeBron James). Fourth among active players in Defensive Rebound Percentage. From 1997-2010, didn't finish outside the 10 in player efficiency save one year, finished in the top 5 nine of those years. Second among active players in blocks per game (2.2), trailing only Marcus Camby.
I could go on but I won't.
--
TheRock ~ Slow dramatic zoom-pan. Doesn't phase the hooded man.
"You have issues." - MWC. Pot. Kettle.