We've already touched on Jose Mourinho's comments about David Luiz, but there's room to go into a little more depth, because they're so interesting. And spot on, too:

For me, Luiz is a central defender. I think he has an important quality for the football we want to play, which is to build. He's comfortable using the ball from the back. In this aspect, he's very important and different from the other central defenders. He can improve, everybody can. From a defensive point of view, he can be much more effective, much more solid. But, for me, the potential is incredible, amazing. He has to play always. -Source: Telegraph.

Ever since he signed from Benfica, we've been hearing that David Luiz isn't a defender, and that holding midfielder might be his best position. And no, he doesn't fit into the centre back stereotype, especially in England, where a player like Gary Cahill is heralded because of his... well, I'm not really sure. Possibly because he's big and loud and jumps around a lot.

David Luiz, meanwhile, is a bit of a basket case. That's undeniable, and the fact that he doesn't look like a centre back makes his screw-ups more memorable in the eyes of many. It's almost incredible how much a players' looks affect his perception -- people still think Thomas Vermaelen is competent, mostly because it looks like he's thinking of ripping your heart out and eating it whenever he plays -- and David Luiz is the victim of anti-happiness profiling. He's prone to spectacular mistakes, yes, but they're not actually any more common than Branislav Ivanovic's, or John Terry's. And I've already been mean enough to Gary Cahill for one post.

"He has to play always"

Mourinho, refreshingly, doesn't gloss over those mistakes. They exist*, and David Luiz needs to work them out of his game to fulfill his potential. But he doesn't let them define the player, and goes so far as to declare him a first-choice starter. He has to play always. Why? The answer is what it's always been -- David Luiz gives Chelsea something no other defender does: He's a quality, if error-prone centre back who also doubles as a deep-lying playmaker.

*Although some see more than others.

Happily, his qualities in that regard are no longer in question. David Luiz's quality on the ball is part of what makes the possibility of a permanent switch to midfield to tantalising, but in truth his ability to dictate play from deep is more valuable as a defender than in the centre of the pitch, because it allows Chelsea to run more options in front of him.

David Luiz is already a clear starter for Brazil, and he's been a first-choice centre back at Stamford Bridge for two straight seasons. He has his limitations, but they're nothing that can't be fixed, and what he brings to the team simply cannot be taught. The idea of Mourinho working with him to iron out the wrinkles in his game while reinforcing his strengths rather than just pushing him into the midfield and letting him run around a bit is absolutely mouth-watering, and could easily turn one of the Premier League's better centre backs into a truly elite one.

Not Mourinho's kind of player? Hardly. Anyone paying attention to the Special One's career will know how highly he values disruptive players, those who can do two jobs at once and so create overloads elsewhere. Contrary to what we've been told this summer, David Luiz is exactly Mourinho's kind of player.