I don't get this thread. Duncan's game is based on skill, not physical ability. His being tall allowes him to work on moves without having to worry about outjumping opponents. He's got a lot left. San Antonio's problems lie in Ginobili who relies on physical ability and the decline of numerous role players. Their defense has been declining as of the last few years too, perhaps due to bowen slowing down and leaving.
They need to rebuild around parker and duncan.