Borussia Dortmund manager Edin Terzic said Thomas Tuchel's appointment as Bayern Munich manager forced his side to change their preparation for Saturday's 'Der Klassiker' clash.
Dortmund travel to Munich one point clear of Bayern at the top of the Bundesliga table.
Speaking at the pre-match press conference on Friday, Terzic said the firing of Julian Nagelsmann in favour of the former Dortmund mentor "obviously changed our preparation a little bit" for the top-of-the-table clash.
"We don't know how much Thomas Tuchel will continue on with what Julian Nagelsmann did in the last few weeks, or whether he brings in completely new ideas.
"But what hasn't changed is that they still have a top manager on the bench and a top team on the field."
Terzic admitted his side had watched "the first six games of Thomas Tuchel at Chelsea" to get an idea of "what could happen in this situation or that".
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The Dortmund coach praised Tuchel's ability to "bring Chelsea together in just a few months and be rewarded by winning the Champions League at the end of the season".
"He's one of the best managers in Europe and one of the most successful."
Terzic spoke publicly for the first time on Nagelsmann's sacking, saying "I find it to be a real pity what happened with Julian Nagelsmann, who's an absolute top coach."
"But we know how quick things can go in football."
Dortmund have not won in Munich in the league since 2014 but Terzic said "we're a different side" this year.
Terzic said on Friday several players would return from injury for the clash, including goalkeeper Gregor Kobel, midfielder Julian Brandt and forwards Youssoufa Moukoko and Karim Adeyemi.
Terzic confirmed that there were "question marks" over English teenager Jamie Bynoe-Gittens and Germany defender Nico Schlotterbeck for the game, while USA forward Gio Reyna and Belgium defender Thomas Meunier have been ruled out.