Berlin - At 29, Julian Nagelsmann is the youngest coach in Bundesliga history and insists his high-flying Hoffenheim can topple league leaders Bayern Munich - the club he turned down - on Saturday.
Eyebrows were raised in February when Nagelsmann, then aged just 28, was made head coach of Hoffenheim.
The appointment was a "a crazy idea", mused the Frankfurter Rundschau daily, while Hoffenheim's local paper branded it a "PR gag".
His only previous experience as a head coach had been of the club's under-19 side, whom he led to the 2014 German age-group title, even though he was less than 10 years older than his players.
But after predecessor Huub Stevens walked away due to heart problems, a drastic remedy was needed for Hoffenheim's position in Germany's top flight - 17th and second from bottom.
Nagelsmann secured a point in his first game with a 1-1 draw at Bremen and kept Hoffenheim up by the skins of their collective teeth last season.
They are a revelation this campaign.
After nine league games they are unbeaten, third in the table and only four points behind the mighty Bayern.
Now Nagelsmann, the youngest coach in Europe's top leagues, is confident of Hoffenheim's first win over Bayern - after 16 failed attempts - at Munich's Allianz Arena this weekend.
"They are the best team in the football league but we are going to be successful against them," said Nagelsmann.
"The preparation for the match against the best German team is very complex. But on the other hand, the football community in Germany doesn't expect much from us, which can be beneficial psychologically.
"We're not going to go to look at the scoreboard and just not let ourselves be slaughtered." .
At 1.90 metres the former defender cuts an imposing figure on the sidelines.
When Bayer Leverkusen's coach Roger Schmidt, 49, berated Nagelsmann during Hoffenheim's 3-0 win a fortnight ago, the younger man kept his head while the elder one lost his.
"What sort of a nutter are you?" Sky microphones in the technical area caught Schmidt yelling at Nagelsmann, earning the Leverkusen coach a two-match ban.
"Kiss my arse. Do you think you invented football?" What Nagelsmann has invented is a winning formula for Hoffenheim.
He does not shy from taking risks.
With Hoffenheim leading 1-0 against Hertha Berlin last Sunday, Nagelsmann turned to his bench in the last five minutes.
He opted not to protect the slender lead, but to try to double it with a three-man attack, swapping striker Adam Szalai for a midfielder.
The gamble paid off, Hoffenheim won 1-0 to leapfrog Hertha into third.
A knee injury in 2008 while playing for Augsburg's reserves ended Nagelsmann's playing career aged 20 before it really got going.
Borussia Dortmund coach Thomas Tuchel, who trained Augsburg's junior side at the time, saw his potential and had Nagelsmann scout opposing teams before giving him a job as assistant coach to the youth team.
"I am very grateful to him for giving me the idea to become a coach," Nagelsmann said of his mentor.
"But he was not my father, our relationship was too pragmatic for that." .
Stints coaching the youth teams at 1860 Munich and Hoffenheim followed.
Nagelsmann led Hoffenheim's U19s to the 2013-14 German championship title, and the final the following year, which put him on Bayern Munich's radar.
Bayern made him an offer to coach one of their junior teams, but he turned them down, preferring to continue learning at Hoffenheim rather than the pressurised environment of Bayern, who demand success.
Comparisons have been made to Jose Mourinho, who received his first break aged 29, working with en-England coach Bobby Robson at Sporting Lisbon, and Nagelsmann has been nicknamed "Mini Mourinho".
Having studied business administration before switching to graduate with a degree in sports science, Nagelsmann qualified with the highest possible mark when earning his German FA (DFB) coaching licence.
His success this season has come with a squad which lost Germany's Kevin Volland to Leverkusen, but signed Darmstadt's proven goal-scorer Sandro Wanger and uncompromising midfielder Kerem Demirbay from Duesseldorf.
Nagelsmann is part of a new generation of German coaches who have adopted the "gegenpressing" tactics - high, intense pressing of the opposition when they have the ball - that are Jurgen Klopp's signature.
During the second-half against Hertha, Berlin's Per Skjelbred was presurised into losing possession three times by Hoffenheim midfielders near the halfway line and the ball was quickly moved forward.
However, Bayern's star-studded midfield will provide a far tougher test and not succumb so easily to Hoffenheim's hard work in the middle.
"There's a hint of Champions League in the air," magazine Kicker wrote last week.
But any Hoffenheim fans dreaming of Europe need only think back to 2008/09, when their team finished the first half of the season top, only to end up seventh in the table.
And club backer Dietmar Hopp is aware Hoffenheim may not keep Nagelsmann past 2019, when his contract expires.
"It looks as, for such a huge coaching talent, the time will come when Hoffenheim will become too small for him," said the 76-year-old billionaire software entrepeneur.