I would trade anyone not named Tatum, Brown, or Nesmith. Borderline untouchable is Williams III but I can see him being a trade chip that nets something worthwhile.
The Celtics desperately need knockdown shooters like Miami, Philly, Milwaukee, Atlanta, and Brooklyn have. Maybe Nesmith can grow into that. Maybe Pritchard can. But they need as many as they can get. And somehow they need to not absolutely stink on defense.
I think it's time for Smart and Kemba to go.