I think Eintracht frankfurt will not make it difficult for Leverkusen because in their first meeting this season Leverkusen easily beat Eintracht frankfurt so there is a big possibility that Leverkusen will be able to maintain their performance to be unbeaten. Leverkusen only maintains their performance so as not to lose because any result will not have a big impact on Leverkusen in the Bundesliga. These two teams both achieved draws in their previous matches so in today match both teams will definitely be aiming for a win to improve their performance at the end of this season.
In my opinion, Leverkusen is only focusing their energy on the European league because they are one step away from qualifying for the final. For me, Leverkusen performance this season has been perfect both in the European league and in the Bundesliga. Leverkusen will play at home in the second leg of the European league and of course they are quite the favorites to win with easily.
Frankfurt hosted Hoffenheim weeks ago and the game ended with a convincing victory even though with very little margin of goals in favor of Frankfurt. They have this season been a good competitor to teams and they've sometimes strived to surprise big teams too. They're a good side and they've been able to stay in shape in the league too even though they're not really standing buoyantly on the league table.
Leverkusen also have been impressive in all rounds and it's not surprising that they're now better than some already grounded teams. It only means that Xabi has a unique managing quality which can be of essence in bigger teams too. I believe he's still got good plans for the German team, which will still be manifested good. In the Europa League, there's been top contending teams from the start till the current stage of the contest.
One would expect that there'll be a heavy difference in their performances and this would cause them to finish very much well in a couple of weeks to come but as it stands, their performance rate so far has been fair and it's best they stay at that pace. Few weeks left and not much impact can be made other than maintaining the tempo and not going below it. We'd see how the both teams will hold up themselves till the game ends.