Mertesacker said: "We have to go for two perfect games against them. We know we can beat them now, so maybe mentally we are in a better condition that last year.
"We respected them too much in the first leg then, so it was too easy for them.
"Maybe we have learned something from those lessons and will do better this time.
"Now we have another chance - and an opportunity to beat the champions. We want to achieve something exceptional this season, so we have to beat the best.