~Snip~
Usually when a strong team that rarely lose, but they're lose in important match, their performance will keep declining and become mediocre (see Liverpool). Maybe Leverkusen will follow Liverpool's path since Leverkusen is one season wonder team, black horse team really rare can being consistent for more than one season (see Napoli).
The upcoming match DFB Pokal is against weak team, so Leverkusen will not have any problem, we will see their performance in friendly match.
There is no guarantee that Leverkusen will follow in Liverpool footsteps after losing an important game, even if that happens to Leverkusen, it won't have a bad impact on them because the season has ended. Leverkusen only has one official match left this season when they face Kaiserslautern in the DBF Cup Final, Kaiserslautern relatively weak strength is not too difficult for Leverkusen to beat their opponent. The defeat to Atalanta in the Europa League Final was very painful for Leverkusen because they failed to maintain their chances of winning the Treble Winner this season. Leverkusen will certainly learn from their mistakes to win their second trophy this season.