You either want your central defenders both to defend, or to have one as a stopper and one covering for him. I've never really seen people successfully use Ball-Playing Defenders (although I'm sure they do), so your best bet is either central defenders or limited defenders; the latter really only belong in more defensive tactics where you're trying to sit deep and you've got a defensive midfielder or two sitting in front of them to prevent your opponent's attacking mids and deep-lying forwards from cracking off long shots from the edge of the box.