To be honest, I think we lost this tie because our physical condition. Speed/quickness/muscle lost us. They were too strong and quick for us.
Also their offense was quick which is the worst poison for us. Good countering team.
There is truth in that too. I watched Frankfurt vs Betis and Frankfurt overrun Betis too in those games. And if you watch Betis in LaLiga they are one of the fitter sides.
So we should have foreseen the physical effort they would put in and look to either match it or exploit it.
We have had a week were Villarreal outplayed Bayern in the first leg and knocked them out, and Frankfurt outplayed Barcelona in Lager Neu and knocked them out. So there are ways around the physical differances if you can technically and tactically outwork it. So we can't take it linearly when a weaker German side knocks out a better Spanish side- or vice versa.
Coming from the first leg the majority of the comments from the team were about the poor grass in Frankfurt. From there I really think that the team put the first leg score down to external factors and overlooked Frankfurts actual quality.
For example, in the first leg, the tie changed in our favour when FdJ came on, yet this leg Xavi still insisted on having him benched. Xavi still sees the central midfield as Pedri+1 because of Pedri's on the ball quality, but it should be FdJ+1. And especially in a physical game - mandatory to be.
And that's why for me were sitting knocked out now. Xavi thought what didn't work in Frankfurt would work in Lager Neu because of the perfect length of grass, the bigger pitch and the not-so-home crowd.