Can Chelsea boss Thomas Tuchel build on 12 months of success at Stamford Bridge?

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.

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