Thomas Tuchel arrives at Paris Saint-Germain with a reputation as a brilliant tactician, albeit with a difficult side.
Tuchel had been unemployed since Borussia Dortmund sacked him last May - just days after the team won the German Cup final.
The 44-year-old was axed after falling out with Dortmund's CEO Hans-Joachim Watzke and losing the support of the dressing room.
He publicly disagreed with Watzke over whether the team should have played a Champions League quarter-final the day after a series of bombs blasted the team bus.
His players then also turned on him after Tuchel left out stalwart midfielder Nuri Sahin for their 2-1 win over Eintracht Frankfurt in the cup final.
In his two years at Dortmund, it was the only silverware he won in Germany as his side was unable to loosen Bayern Munich's grip on the Bundesliga.
By his own admission, Tuchel can be a challenging personality.
"I wasn't easy to deal with as a player," he admitted in a 2009 interview.
Like his role model Pep Guardiola, Tuchel is not afraid to switch formation or tactics two or three times during a game, making it impossible for opposing coaches to second-guess him.
He can be prickly in post-match press conferences and toys with questions which are not to his taste.
A knee injury cut short his playing career as a defender at third-division Ulm in 1998 and Tuchel turned his hand to coaching.
He cut his teeth in the youth academies at VfB Stuttgart and Augsburg.
His career took off at Mainz where he was promoted from Under-19s boss to first-team head coach two days before the start of the 2009/10 season with no Bundesliga experience.
"We had a rule-breaker at Mainz. The club manager Christian Heidel, who had the courage to make me a Bundesliga coach," Tuchel later said of his shock appointment.
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Tuchel turned out to also be a rule-breaker.
Working with an annual budget dwarfed by Mainz's Bundesliga rivals, Tuchel succeeded by insisting on high-tempo, attacking football.
He shuffled his side constantly, choosing his team based on the best way to exploit opponents' weaknesses.
Tuchel believed Mainz could only survive in the league by playing in a variety of styles, making them unpredictable for their rivals.
His side set a Bundesliga record by winning their first seven games of the 2010/11 season.
"We didn?t want to break rules for the sake of it," he said.
Tuchel helped nurture talent like Andre Schuerrle, whose cross Mario Goetze converted for the winning goal in the 2014 World Cup final.
Mainz finished seventh in the 2013/14 Bundesliga, but Tuchel walked away with a year left on his contract, saying he had taken the team as far as he could.
Mainz had twice reached the Europa League and held their own against Germany's top clubs.
Just like Guardiola did before him after his time at Barcelona, Tuchel took a year's sabbatical after leaving Mainz.
When Jurgen Klopp announced he was leaving Dortmund in 2015, Tuchel was ready to follow in his footsteps from Mainz to Dortmund.
You could not get two more contrasting characters.
The unshaven Klopp's rock and roll, fist-pumping style on the sidelines was juxtaposed by the clean-shaven, brooding Tuchel.
Before Klopp left, he warned Dortmund's fans about making comparisons between his success and the new boss.
However, Tuchel built on Klopp's accomplishments, steering Dortmund to second and third in the Bundesliga, securing Champions League qualification in his two seasons.
The bomb attack on the Dortmund team bus in April last year triggered the events which led to his exit.
Tuchel was onboard when three bombs hit the team bus on the way to their Champions League quarter-final at home to Monaco.
The game was initially postponed, then played less than 24 hours later when the shell-shocked hosts lost 3-2, and Tuchel was left fuming.
He complained that he was not consulted about whether the match should have taken place.
Watzke refuted the claim and it was just a matter of time before Tuchel was forced out.
"Our biggest disagreement came because I was on the bus and he was not," Tuchel said in court in March during the trial of the German-Russian accused of the bomb attack.
"There were differences in the way he dealt with me, even without blaming him."
Thomas Tuchel will be expected to transform PSG into giants both at home and in Europe