Second-placed Leipzig head to Munich two points behind leaders Bayern, who have not lost at home in any competition for over a year.
"In some situations, Bayern don't seem quite as keen, no longer quite as focused," due to this season's dense fixture list, Nagelsmann said on Friday.
Nagelsmann's men then host Manchester United on Tuesday with a last 16 place in the Champions League at stake.
First up, Leipzig will try to earn their first win in Munich at the fifth attempt having yet to score at the Allianz Arena.
Leipzig can usurp Bayern as league leaders, "but that doesn't mean we are on an equal footing," insisted Nagelsmann.
"We have a good plan, the boys are up for it, but it will still be very difficult," Nagelsmann added.
Bayern striker Robert Lewandowski, who has already scored 15 goals this season, and goalkeeper Manuel Neuer were both rested for Tuesday's 1-1 draw at Atletico Madrid in preparation.