While I see Duncan as PF, I have no problem with the argument that Duncan is a center for a couple of reasons:
-Duncan played center in college, and if he was drafted to any other team other than San Antonio(he was predicted to go to Boston) he would of been a center
-Olajuwan was the same as Duncan, drafted as center, played power forward with Sampson(albeit it can be argued Sampson was PF), then took over the center position like Duncan if that Basketball Reference stat is to be believed. I will take Olajuwan over Duncan if he can be considered a PF on the same premises...
-Duncan guarded the oppossing centers majority of the time after Robinson retired( guarding Shaq in 03)
-Young Duncan was PF in that his FACE game and back to the basket game reflected the average PF game at the time, late 1990's.
To me Duncan is the Rich Man's Brad Daughtery(no slight to Duncan, just who his game and movement resembles the most), and Daughtery was clearly a center...