Tiago, Kawhi and possibly Danny Green are pretty much the "must haves" as the Spurs move forward. Blair seems to be a gone goose, and Neal's skills as a gunner can be replaced.
Manu and SJax are the big questions. Both are important pieces right now, but each faces diminishing skills and longer injury stretches. Manu is here for as long as he wants, but the TD pay cut on his latest contract should set the tone for these two as they negotiate new deals.
It'll be interesting to see how the Spurs eventually handle Joseph and Mills.