There's been two developments in the past ten days that have swayed me into thinking that Smith will be their primary target.
1) Blair appears to be on the verge of taking at least a relatively significant step forward and if he does, then it makes no sense to surrender depth of assets for Millsap or pay him roughly $10M annually when they could retain their depth and pay Blair $6-7M less.
2) Splitter's paper cuts are beginning to mount. At this point, they've got to be thinking long and hard about whether this is someone they want to pay at least $6M annually to on a long term contract going forward.
I'm not saying the Spurs can offer the best value for Smith, but the pieces do fit: Smith, Pachulia and Stevenson for Jackson, Splitter, Bonner, Blair, Joseph, draft picks and possibly overseas rights.