Bringing in a Stiemsma or Withey to solve shot-blocking situation is ... solving 1 problem at the cost of creating 10 new problems. Highly flawed third string quality specialist shot-blocking centers are not an answer to Boston's situation.
Boston needs a a quality basketball player capable of being a starting caliber center.
Edit: It is like Bryan Colangelo (Raptors) bringing in Reggie Evans to solve their rebounding problems. Yes, Reggie rebounded the ball well but he sucked defensively and he was abysmal offensively so the team got worse. Solve one problem, create several new problems. A specialty of Mr Colangelo while in Toronto. He did the same thing with Jason Kapono. Raptors need 3 point shooting. Problem solved, hire best 3 point shooter in league. Nevermind that he can't defend a chair or rebound the [dang] ball. Irrelevant. He can shoot 3s and that is what the team needs. Solved problem, created several new problems. Team got worse.