Krstic, Murphy... it's all the same, they shouldn't be on the floor. What's exactly the point?
Length? Those guys don't block shots or protect the rim, disregard how long they are. Lenght by itself doesn't matter, it's what you do with it. And these two do very little. They won't take their much smaller defender to the low blocks and collect points with post-ups. They can't and won't do that.
You're putting yourself in trouble defending the transition, having worse help defense because they're so slow, giving their perimeter bigs some good looks from the 3 point line or driving lanes or open paths to cut and all those transition shots to gain exactly what? It's just a mismatch in their favour.
They benefit from superior speed and quickness, Boston won't benefit from the superior size because those guys don't really play "big".
There's only one reason to keep them on the rotation (besides having them matched with NYK conventional 5s).