Hate to drag up the past, but remember when Steve Michaels had the yips in defence? One person was literally responsible for us leaking 50-odd points, with a couple more big scores put on us too.
It just takes one liability to totally destroy the defensive confidence of a team. Having two halves that are dodgy defense-wise means both of our edges will be targeted - either the outside defenders come in to help, exposing the wingers, or the middle forwards have to follow the ruck closer, meaning one side of the ruck will constantly be loose.
Bad bad bad bad.
I may be overconfident in this, and I'm definitely in the minority, but Opacic looks to me to be defensively very solid (If he gets his shoulders right). He might be who we're looking for. There just don't seem to be any Matt Cooper type players these days who gun it on both sides of the football in the centres.