Al is clearly a 5, and he has been his entire career. So it's not surprising that he's struggling now trying to play the 4.
He's got to realize that he's hurting our defense significantly with his lack of quickness and foot speed when going out to cover stretch 4's, as evidenced by the last half dozen games or so, especially the Cleveland game where Love abused him.
I prefer JJ to KO in the starting lineup, but I support any move that moves Horford back to his true/natural position at center.
EDIT: Of course, I'm willing to let Horford play the 4 under the condition that we get a significant upgrade at center (like Boogie) or we get a more mobile center like Noel who can cover the quicker 4's out on the perimeter.