Spurs just don't have much room to make the kind of improvements needed.
There aren't too many open roster spots. Barry and Vaughn are still under contract, there's little chance of them getting bought out.
The only youth so far you can count is Mahinmi, and there's no guarantees he gets any chance from Pop whatsoever.
Their 08 first round pick is up in the air. If they draft a euro, he stays overseas to either never come over or get traded. If it's an NCAA product, their history the last decade or so indicates they'll blow it on someone who isn't an NBA caliber player that can help this team.
Viktor Sanikidze who was drafted ahead of Trevor Ariza can't get anything beyond a summer league invite.
No team will collude with them like Memphis did with the Lakers.
They have no cap room larger than the MLE, and the free agent class is poor. Maybe they can do sign-and-trade Van Horn type deals with Horry or Finley or Thomas, but the pickings are slim.
Splitter was the key. Not because he was going to be a star, but because at worst he would likely have been a rotation playing big man on a cheap contract allowing the Spurs to best spend their limited resources elsewhere. Now that's likely done.