It's not just size. Also slow and poor defensive application.Yes, because he’s undersized. He’s useless in defence. You need to have a solid backline around him to make the most of his abilities. But when your backline sucks, he’s not going to help you in any meaningful way—outside of taking kick-ins and, once in a while, delivering a nice kick from the half-back line that might set something up.
Biggest issue is he could at least man up and pressure. Just drifts free even when swans have the ball.
Wizard is also small.