It appeared to be a desperate throw of the dice by manager Antonio Conte, a last-minute swoop for defensive reinforcements on transfer deadline day after missing out on Napoli's Kalidou Koulibaly and Roma's Kostas Manolas. Luiz's erratic performances for Brazil in the 2014 FIFA World Cup were still fresh in many people's memories, and the arrival of a seemingly error-prone defender was not seen as the solution to Chelsea's ageing back line.

Five months later, the 29-year-old has turned from club clown to defensive rock. He has reinvented himself as the cornerstone of the most miserly defence in the Premier League and has swapped his reputation of being an unpredictable liability for one of composure and responsibility.

It has been quite the transformation, though in truth Luiz was never as bad as the image portrayed of him. Yes, he was prone to the odd brainless moment, but his mistakes were always magnified while his good performances were often overlooked. Towering displays such as defending impeccably for 120 minutes in the 2012 Champions League final and then scoring in the victorious penalty shootout despite not having played for over a month due to injury have generally been forgotten outside of Stamford Bridge. Perhaps it's the hair or his larger-than-life persona, but Luiz has always attracted a negative spotlight in England.

Now, though, opinions are changing and deservedly so. He has introduced a consistency to his displays that demands attention, with his decision-making being the most noticeable improvement in his game. Out have gone the rash challenges, in have come timely interventions. His reading of the play in front him and the way he compensates for his fellow defenders' mistakes have both been excellent.

The player himself would surely be the first to admit that he has been helped enormously by the change in system at Chelsea. Flourishing as part of the back three installed by Conte after the team fell three goals behind at Arsenal in September, he has been reinvented along with the rest of the defence.

Luiz's ideal role had always been a cause for much debate. Too cultured and attack-minded to be in a back four but not disciplined enough to be a holding midfielder, it seemed this magnificently gifted footballer would be left failing to fully realise his talent. Now that he has slotted seamlessly into a back three it seems crazy that nobody thought of it earlier, even if 3-4-3 and 3-5-2 systems haven't been in vogue in English football since the 1990s.

The faith placed in him by Conte has seen Luiz assume the senior role in the back line, even if Gary Cahill is the one who actually wears the captain's armband. Luiz has always been vocal on the pitch, but his instructing and cajoling are more obvious now. In last Saturday's 3-1 win over Arsenal, for example, he could be seen giving Victor Moses a quick-fire lesson on how to press the man in possession after Theo Walcott had found a rare piece of time and space in the Chelsea penalty area.

While he might be more content to do the simple things these days rather than attempt a Johan Cruyff turn on the edge of his own box, Luiz's new position still allows him to satisfy his more creative urges. His wonderful vision and passing range means he can launch attacks from deep either by playing penetrating balls through the opposition midfield or delivering over the top. A smartly taken free kick last weekend that caught the Arsenal defence cold might have ended in Eden Hazard being one-on-one with Petr Cech in the first half only for it to have been fractionally over-hit. With two centre-backs alongside him and the added insurance of a brace of defence-minded midfielders in front, Luiz can also embark on the occasional rampaging charge upfield without too much concern.

Such has been his influence behind Chelsea's nine-point lead at the top of the table that it is hard to think of too many better central defenders in the Premier League right now. Cesar Azpilicueta is a contender, as is Tottenham's Toby Alderweireld, but that's about it. Given the question marks that surrounded him when he re-signed for Chelsea on Aug. 31, that is a remarkable makeover.