Considering even though they've played like crap, yet they are still a top half of the league team in points allowed, assists allowed, steals (top 5), blocks, Opponents turnovers (top 10), and of course Free Throws Allowed (#1) and of course 2nd in point differential, I'd say they have a pretty good ceiling. Unfortunately their just out of it in opponents Field Goal % and are almost at the bottom of opponenets 3pt%, due to their out of sync rotations.
The Spurs usually gain ground on defense by leaps and bounds after the All-star break, so they shouldn't finish any lower than 11th or 12th, and will probably finish somewhere in the top 10.
Their ceiling is probably top 5, but it would take a miracle for them to come together enough for that this year.