The David Luiz conundrum is the second biggest concern for Chelsea fans, only just behind Jose Mourinho's treatment of Juan Mata. Since arriving at Stamford Bridge in January 2011, Luiz has become a cult hero amongst the Blues supporters with his mop of curly hair, epic penalty run-ups and excellent defending when he's on top of his game.
That last point is the reason for concern around his future at Chelsea. There is no doubt that Luiz has the talent to become a world-class defender, but his tendencies to drift out of position and dive into rash challenges make him the antithesis of a typical Mourinho centre-half.
The Special One prides himself on constructing a solid defence, with at least two players covering the keeper at all times. Luiz's lapses in concentration have cost Chelsea crucial points this season, and his disorganised display at Newcastle United led to him being dropped from the side for a lengthy period.
Now that he's back, the question remains as to whether he can become the type of player Mourinho wants him to be.
Luiz thrives under the burden of responsibility, and his best performances have come in big games. He also plays better when paired with Gary Cahill, as he takes the initiative to organise the defence.
His forward forays are not a problem in themselves, as long as one of the full-backs stays back to cover his absence. His tackling is improving, as is his decision-making, but it appears that he is suffering from overconfidence on occasion.
Luiz has become a guaranteed starter for the Brazilian national team and has even captained La Selecao. According to The Express, Barcelona sent Dani Alves and Neymar to convince him to join them in the summer, an offer that he himself firmly rebuffed.
The fact that all this has happened when he is just 26 years old is a remarkable achievement, and nobody could blame him for letting it get to his head.
What Luiz needs to do to ensure that any future offers for his services are emphatically turned down is simple. He needs to get his head down, work hard and concentrate fully for the whole 90 minutes whenever he gets his chance. As much as he enjoys performing on the biggest stages, he needs to prove that he can put in a shift against smaller clubs to stand a chance of regular selection.
It's widely accepted that he has the potential to take over the captain’s armband when John Terry retires, but he will need to win Mourinho over quickly if he wants to stay at Stamford Bridge long enough to see that happen.