New Bayern Munich coach Thomas Tuchel acknowledged Saturday he faces a challenging start to his new job after his surprise hiring Friday to replace Julian Nagelsmann.

Tuchel goes straight into crucial games, starting with German title rivals -- and Tuchel's former club -- Borussia Dortmund on April 1 (stream live on ESPN+ at 12:30 p.m. ET).

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"The challenge can't be any greater," Tuchel said.

Ten days later, Bayern play Manchester City in the quarterfinals of the Champions League.

There will be little time to rest or practice new tactics, with many Bayern players currently away with their national teams and then seven games in the first 22 days of April.

"I was relatively naive in the first conversation [with Bayern]. In the first 30 seconds I didn't know what we were discussing or what it was about," Tuchel said.

Once it became clear Bayern wanted him to take charge immediately, "it occurred to me that it actually begins right away with Dortmund with an international break beforehand."

Bayern against Dortmund is "the" game in German soccer, he added.

Tuchel said the move came as a surprise and that as recently as Tuesday he had no contact with Bayern. He imagined his next job would be outside of Germany, he added, but that he had been following Bayern's season with interest.

Tuchel hasn't worked in Germany since 2017. When he left, the only major trophy he'd won was the German Cup with Dortmund. He returns having won two French titles at Paris Saint-Germain and the Champions League and Club World Cup with Chelsea.

Bayern can still win three titles this season -- the Bundesliga, the German Cup and the Champions League.

Consistency is a concern after Bayern chief executive Oliver Kahn highlighted that as a reason for getting rid of Nagelsmann.

Bayern are likely to be looking for Tuchel to get the best out of players like Leroy Sane and Serge Gnabry, whose form has dropped off this season, and Sadio Mane, who has rarely been at his best in an injury-disrupted season since joining from Liverpool.

Sporting director Hasan Salihamidzic said the club backed Nagelsmann as concerns grew over the team's performance but decided on a change at a meeting Monday, a day after a loss to Bayer Leverkusen cost Bayern the Bundesliga lead.

"When you see that this curve of performance is going down, you're forced to react," he said, when asked if Bayern had reacted to the possibility Tuchel might take a job elsewhere. "Fortunately, there was a top option on the market and it happened quickly."