I think that today it is very much possible, that Bayern Munich will not win their match against Bayer Leverkusen. In the last few games Bayern Leverkusen was in a very good shape both in the Bundesliga and also in the Europa League. Leverkusen has a very talented squad with a lot of young players that have a huge potential. If they are feeling well and confident they can be dangerous to every other club. In addition to that Leverkusen is playing at home, so this is another small advantage for them.
That being said, Bayern Munich is stil the strongest team of the Bundesliga by far and if everything goes relatively normal, then Bayern should win today too, but you never know.
I think Bayern is more fresh,I mean Bayern Munchen and when they are at a better physical condition they usually can win games,I doubt that they will not win in the game of tonight as any result except win here puts their campaign to win the title in danger,yesterday Dortmund showed that it was only a mistake that they made against Schalke and it won't happen again.
Bayern Leverkussen despite winning easily at Ferencvarosh in Europa League they have played at Thursday night which will make exactly 3 days when the game between them and Bayern Munchen starts,so physically speaking Bayern Munchen should win easily this game.