David Luiz has been a confounding presence at Stamford Bridge ever since he set foot on the hallowed turf in February 2011.
He has given much to the Chelsea faithful since his two arrivals from Benfica and Paris Saint-Germain, including egregious errors, outrageous efforts on goal, stoic blocks, wondrous passes, five trophies and £50m (or a net loss of around £2.5m, depending on how you look at it).
In any case, he's been divisive. And, after his 25-day-late Halloween house of air-kick horrors instillation against Spurs at Wembley, the Brazilian was back to his best against the Premier League champions on Saturday.
The problem with Luiz, and there is undoubtedly a problem, love him or hate him, is that you never know which one is going to turn up.
Will it be the absent, permeable, invisible presence that we've seen countless times or the totemic, body-on-the-line, eyes-on-the-prize master distributor that we've seen slightly less times, but has undoubtedly turned up in big moments - the Champions League final being one of them.
Many managers have garnered tumultuous, hero-to-zero, pendulum-swinging performances from the 31-year-old. He's an enigmatic character, capable of executing tactical masterplans for 89 minutes before undoing it all with one flailing, foolish swoop of a right boot.
But, on Saturday, in his finest hour at the helm of the Blues to date, Maurizio Sarri showed why he is in fact a master defensive tactician.
Even at the highest levels, calibration is required. Mistakes need to be made for lessens to be learned. The mistake in question was made on that fateful night at Wembley *shudder*.
The lesson? You simply can't let Luiz and Antonio Rudiger be picked off on the counter by pacy, ethereal players. And so, faced with a front three of Riyad Mahrez, Raheem Sterling and Leroy Sane - I think that satisfies both categories? - Sarri needed to ensure a repeat drubbing was not in order.
Whereas against Spurs they dominated possession, looking to take the game to their north London counterparts, against City they utilised a quasi plan b. Not that the plan was implicitly to be suffocated for nigh-on 44 minutes before breaking to score with their first shot on target, he would've surely wanted a bit more football to be played, but there was a concerted effort to not be stretched by Pep Guardiola's torchbearers.
And they weren't. Of course, there were hairy moments in that first half - there always will be against a side of that unrivalled (at least in England) quality. But the Blues' rearguard was never caught on the hop, and rarely allowed Mahrez, Sterling and Sane to use their ample afterburners.
Because of the way Sarri's side initially packed themselves inside their own half, and the everlasting industriousness of N'Golo Kante and Pedro in particular, David and Bernardo Silva found themselves unprecedentedly nullified. The triangles and interplay that they so often thrive on to bamboozle opponents across the land were not on the cards.
Thus, City found it difficult to get the ball to their front three without clipping balls from side to side, meaning any space that had been created was snuffed out by those extra few seconds required for the flight and subsequent control of the ball. And, when these were wayward, it was more often than not Luiz who barrelled in to get the clearing header away.
In fact, such was the starkness of this that the defender was forced into making just two tackles during the 90 minutes, both of which he succeeded in.
As ever with the long-haired geezer in his more favourable moments, it was not just in the defensive phase that he excelled.
For all the passing verve of Jorginho, in such a game it was always likely that the centre back's enviable ability for inch-perfect raking balls would hold the key to any chance his side could foster, and so it proved.
You can praise John Stones' passing all you want, but he'll never come close to the range, technique or audacity that Luiz possesses on his day. It was a peach of a ball, better than any City midfielder had produced all early evening, and its accuracy allowed Pedro to exploit the space Luiz had spotted without delay.
A few tenacious runs from Willian, Eden Hazard and N'Golo Kante later, and Chelsea were 1-0 up. In the second half, imbued by their snatch and grab exploits, they enjoyed far more front-foot ball and Luiz was again supreme in his guarding of the ball - something which unfortunately could not be said of Andreas Christensen on Wednesday night against Wolves.
And, just as his ball was accurate beyond decree, so was his header that consigned the opposition to their inaugural league defeat of the season, and the onlooking fans into suitable pandemonium.
After a torrid end to last month and a shaky start to December, a leader was needed to haul the Blues out of their slump. After dropping him from the starting XI for the trip to Wolverhampton, Sarri was shown that Luiz could be just that, alongside captain Cesar Azpilicueta, who was true to his title in a return-to-the-pantheon performance.
This was Sarri at his most pragmatic, playing to his defenders' strengths rather than attempting to solely placate his own philosophy. He allowed his side to attain the confidence to play football within the game, rather than manufacture it before kick off and be picked off.
In his post-match, man of the match accepting press conference, Luiz spoke regularly of the "humility" that they showed throughout the encounter - an overt reference to Sarri's previous allusion to the over-confidence in the squad.
Of course, Sarri's ultimate aim will undoubtedly be to have his side playing his football, but for now he can rest easy in the knowledge that he has a worthwhile unit at the back, capable of stumping the greatest attackers on their day.
Now he just needs to make sure he can keep his Brazilian long enough to observe this transition.