Jupp Heynckes explained that Robert Lewandowski was omitted from Bayern Munich's win over Celtic due to an "overburdening", not injury, and is motivated to face Borussia Dortmund in Der Klassiker.
Lewandowski recently spoke of the difficulty of leading the line in three competitions, with Bayern lacking a recognised back-up striker to Poland's record goalscorer.
Bayern boss Heynckes consequently omitted Lewandowski from the squad that won 2-1 at Parkhead in the Champions League in midweek, although he later stated his belief that Lewandowski would be fit to face his former club.
That was a stance Heynckes reiterated at his pre-match media briefing, insisting that he was merely protecting Lewandowski from the threat of injury.
"He has not sustained an injury, but an overburdening," Heynckes said.
"It was a precautionary measure and Lewi is a smart guy who said that if he played again on Tuesday he'd have torn a muscle.
"I'm careful and always on the side of the player, because there is no benefit using players who are not 100 per cent fit.
"You cannot risk anything at all. He has trained well and is back in full strength and is highly motivated."
Bayern have yet to be beaten since Heynckes returned to replace the sacked Carlo Ancelotti and have regained a familiar position atop the Bundesliga thanks to Dortmund's three-match winless run.
Dortmund coach Peter Bosz also saw his side held to a 1-1 draw at home to APOEL in midweek, a result that all but ended their chances of reaching the Champions League last 16.
But Heynckes says Bosz – who was only appointed in the close-season after leaving his post at Ajax – deserves more time to implement his methods.
"First of all, Peter Bosz was a good footballer and when you become a coach at Ajax you have to bring a lot of know-how and he certainly has," Heynckes added.
"I think everyone needs some time to bring in their philosophy.
"Dortmund will be much more concentrated and attentive, their own fans forgive their own players against Bayern. We have seen them play and will prepare according to our play, but it will be up to the players to show that on the field.
"There are no clear favourites for me."
