Spot on. When I think of this defenders theory I always go back to the Manchester United model. Vidic & Ferdinand (in the latter's prime) were an exceptional example of this. Vidic will the be the first defender who will attack the ball, he'll be up there for the first header, coming in with the hard tackles etc. Rio will collect the second ball, he won't necessarily play it out, but he will do the last-man job. You could argue Ivanovic is a stopper, because his ball skills aren't really good and because of his superior strength he's good at the one-on-ones. However even then, I don't trust Ivanovic at centre-back as of late. There's is a general decline of stoppers around right now, because of the way the game's evolved in the last 10years. Chalobah is also a sweeper, as is Bruma. Cahill, as a sweeper, isn't "world-class", he's decent back-up though.