Duncan for the main stay of his career has been used at the four. I think when you debate criteria he's certainly up there with the Karl Malone's, Charles Barkley's and others. He may very well be the best all time. As far as centers, he doesn't hit the top 5. He may be close to the top 12-15. Olajuwon, Ewing, Robinson, Malone, Jabbar, O'neal, Chamberlain, Russell all filter in right there or above. (That list was in no particular order).