Essentially, the Spurs delimna is this...
Tim Duncan isn't really an offensive or defensive force - he's more of a 10 pts / 6 rebound guy who will have spurts of his game of old but for the most part will be average. And, he'll be earning $21 million to do it if a new deal isn't worked out. IMO, the only untradeable asset.
Tiago Splitter really should be THE guy relied upon to score and be more of a defensive presence. If all goes extremely well, he'll be a 15-18 pt / 8-10 rebound a game guy. Expectations will be probably be 12/7 or so...tradeable but one of the last to go if needed.
DeJuan Blair is interesting in that he can really play - can score, gets out and fills the lane on fast breaks and can rebound. Just too much of a liability on defense due to lack of length. Not sure of what he will be expected to contribute and when - can't imagine there will be GREATER expectations of him next year.
Richard Jefferson - could possibly contribute if in a different system (that allows him to be one of the primary options AND if given room to make moves). Since SA doesn't run that system, he's a significant liability in that his lack of defense doesn't justify his playing time or salary.
Matt Bonner - role player, 3 pt shooter. Worth every penny when he's shooting >37.5% from beyond the arc; when he's not, he's a defensive liability. Is being paid to much for such a role.
McDyess - retired.
Ryan Richards - not ready for prime time.
Given those options, I would suggest that the Spurs bite the bullet and just concede to re-building. That would mean they trade DeJuan Blair and some other asset (preferably Jefferson but perhaps Hill, Neal, Anderson or Butler) and pick up a VETERAN defensive small forward. Perhaps a sign and trade for Tayshaun Prince, AK47, Wilson Chandler, whomever.
Next, they should commit to starting TP, Anderson or Butler (whichever one is best and isn't traded), FA SF, Splitter and whomever the Spurs can pick up w/ the 29th pick. Manu would be the 6th man and TD would come in off the bench. Essentially, the Spurs would start 3 "new" people.
That would mean that 1 year from now, they would have a core of TP, Anderson/Butler, FA SF, Splitter and 29th pick w/ quite a bit of cap space once Duncan's salary comes off the books. Another few years and Manu's would come off as well.