Jeremy Sochan is entering the final year of his rookie contract, and he's eligible for an extension. He and the Spurs could have agreed to a deal over a month ago, but for some reason, no deal has been struck. That leads me to believe that they either can't come to an agreement on the details, or San Antonio wants to take another season to determine whether the former Baylor Bear is worth a long-term contract.
Unfortunately, he only has himself to blame either way. Sochan is a stellar defender, but his offense leaves much to be desired.