I don't really want Butler. I suspect he'd clash with IT, and there are a lot of holes in his game.
He's not a great outside shooter, and he needs the ball in his hands a lot.
Still, he gets to the line a ton, he's a really solid defender, he can rebound and pass.
Not a perfect fit with Isaiah, but I think Butler is about as good as the Celts are gonna do in terms of trading for a star who completes the group they've put together.
I think you need to have more than one guy who can take the ball and go get his when you're in the playoffs, anyway. We don't need -- or want -- to have that 3rd star be a purely off-ball type of scorer.