Thomas Tuchel's appointment as Chelsea head coach a year ago has always been laced with intrigue.
Regarded by some as "complicated" and a "perfectionist", the German was described by Borussia Dortmund chief executive Hans-Joachim Watzke as "a difficult person" and Tuchel had fall-outs at Mainz and Paris St-Germain too.
So why would Chelsea, a club where managers do not last long and player power has seen a few off in recent times, turn to him?
Why too would Tuchel, who was initially given only an 18-month contract at Stamford Bridge, take a chance on Chelsea?
Because, as Watzke also said, the 48-year-old is a "brilliant coach". Mainz chief executive Christian Heidel, who worked at the Bundesliga side with Tuchel, says the German is "an absolute perfectionist" and someone "who likes to go very deep - he does not care at all for the superficial stuff".
"I suspect this is maybe the reason why a lot of people think he's complicated," Heidel, who also worked with Liverpool boss Jurgen Klopp at Mainz, tells BBC Sport. "But I've never seen an amazing coach who is not complicated. The two probably go hand in hand."
That blend has certainly worked for Chelsea so far. Tuchel reached the top four and won the Champions League last season, after taking over from Frank Lampard in January, and led his team to an FA Cup final and League Cup final in the space of his first 12 months.
But it is the next year that will perhaps prove crucial as the shine from his appointment begins to fade and he reaches a period where he and Chelsea managers are usually put to the test.
Heidel says "Klopp is naturally charming, he's very extroverted. Thomas is a little more of an introvert and he does not let people come as close as Jurgen would do."
As Tuchel was well aware when he came to London, success is all that matters at Stamford Bridge. But combining trophies and tranquillity has proved tricky for even such former bosses as Jose Mourinho, Carlo Ancelotti and Antonio Conte.
Tuchel has made a decent fist of it, though. Winning Chelsea a second Champions League, by beating Manchester City in the final, earned him a contract extension to 2024, which he wants to see out even if he says "history tells us that it's not that easy".
For now, he says: "I don't want to be anywhere else."
But, more importantly, he has his eyes on a Chelsea future and has taken time to lay some firm foundations over the past year with players, staff and the club's hierarchy.
Despite Heidel saying Tuchel is "a little bit more introverted" than Klopp, he did host a barbecue at his house following the Champions League triumph to thank staff for all their hard work.
And where Lampard, a legendary Blues player, struggled to connect with all of his squad, which eventually led to his downfall, Tuchel's natural communication skills have kept his players engaged.
His ability to bring out the best in Antonio Rudiger, who fell out with Lampard, and reintegrate Ben Chilwell after leaving him out earlier in the season are good examples of this.
Those skills have been put to the test by Romelu Lukaku, however, after the club's record £97.5m signing conducted an unsanctioned interview with Italian TV last month, where the striker questioned his role in the team and Tuchel's methods.
In the media conference that followed, 16 of the 20 questions put to Tuchel were about Lukaku, but he remained calm and composed. He said he'd had "more difficult quotes crop up in my past" and laid down the challenge to his frontman to respond on the pitch.
Whether Lukaku has done that is open to debate, particularly after a poor run of results, and may be the key to Chelsea's fortunes this season.
But deep in that media conference was a revealing insight into how Tuchel tackled the episode - with support from those in the leadership team.
Tuchel's relationship with Lukaku could be key to Chelsea's success
Both Tuchel and Chelsea director Marina Granovskaia spoke to Lukaku about the interview, with the manager describing the talks as "very calm, very quick and very open".
But the fact Tuchel was able to lean on Granovskaia - and has also been reliant on technical and performance advisor Petr Cech - was telling.
Club sources say the German's relationship with directors above him has been better than any recent manager at the club and allows him time to focus on the coaching and man-management of his players.
Trusting those around him is a key value for Tuchel, according to Heidel, who remains in touch with his former manager. Tuchel's assistants are all former colleagues or team-mates from Mainz and have followed him to Dortmund, Paris and London.
He also says success will come if the Chelsea hierarchy can offer him support, while offering enough space to breathe.
"Without saying one is better than the other, Thomas does not let people come as close as easily as Jurgen would do," says Heidel, who also regards Klopp as a close friend.
"It is important for Thomas to have somebody who supports him to the outside media - and supports the way Thomas wants to play football.
"So he needs to feel the trust, but he doesn't need to feel people constantly interfering in his business. If you trust in the way that he works and the way he wants to play football, he's unstoppable. He will get the club all the success he needs as long as people keep all the other stuff off his back."
Tuchel's frustration with the team's recent form - one win in five Premier League games has left them third and 10 points behind leaders Manchester City - has been clear to see on the sidelines. His constant demands on players may yet reveal further issues.
But Sunday's 2-0 win over Tottenham put a smile back on the face of a coach who says he is "awfully impatient" for success. Fortunately for him, Chelsea have a chance to win both the Club World Cup and Carabao Cup in February.
It would crown a remarkable 13-month period for a boss who says he is always looking to the future.
"I have had no time to assess the year and this is maybe very good news because I'm not the person to look back or feel great about the past," adds Tuchel.
"I'm a person to take care of today and to make tomorrow's life easier. This is how I feel good and this is how I work - and hopefully it will be for many more years to come."