The Spurs have only started centers next to Duncan when the center has been a really good player who could handle starter's minutes. So the first six years of Tim's 19-year career he spent with Robinson, who was never going to be benched. After that, Tim was in his prime and like most teams, the Spurs wanted to get a designated defender to take pressure off their star. So enter Rasho and Nazr for three years combined. Then you see them starting to get smaller guys next to him with Oberto, Bonner, McDyess and Blair starting the majority of the next six seasons. Then you finally get a center who can start next to Tim again, and you get Splitter for three seasons. Then you get LMA.
That parallels what I said about what they should do for Aldridge. They got the best big they could and let Tim play the other position. A Tim got older, it became critical that they got a man-defensive center for sure. But they clearly went with shorter guys for years.
Diaw is getting close to the end. He only has $3 Million guaranteed for the rest of his contract. I don't think the Spurs consider power-forward checked off on Boris' account any more than they did last year.
Spurs should be able to afford a max deal to Clarkson (I haven't run the numbers on a $92-Million cap, but it would be REALLY close). And I think both of the other players are on teams that aren't going to surrender their cap space to keep guys who aren't part of their future. They're both looking for bigger fish this summer. I expect the Lakers to match, so a S&T wouldn't be a bad idea. But I think there's going to be a young player the Spurs can get for that money. As I said, they just need to pick the correct one.