The fact is that some teams hardly take preseason matches seriously, so using preseason to fully determine the performances of a team, I don't think, is ideal. It’s very possible for some teams not to do well during preseason, but during the main season, they will perform so well, even more than people expect. In fact, not all key players play in preseason, and one thing to note is that some teams' preseason matches are often against smaller teams. But let's see how Bayer Leverkusen's season will look, even though I don’t think doing well in preseason fully determines their overall season performance.
from the preseason you are going to know whether the club is going to go far or not because they will want to show display of what they have been learning for sometime so i think you will be able to judge from the preseason sometimes, and it is rare to see them not to do well in the preseason and then when the main season starts they start performing well this are part of the reasons and since they are against smaller clubs they should even find it very easy to beat them since they are smaller clubs, its actually very mysterious how some might even show sign of starting well and the next thing they start losing focus. And Leverkusen seems to be ready for the season to kick off.