Even though they managed to end the season as an undefeated team in the Bundesliga, Leverkusen is not yet experienced enough in the Champions League, they must be prepared tactically and mentally to face strong teams such as Real Madrid, Manchester City, Inter Milan and PSG. Xabi Alonso must be able to maintain the quality of his team to face next season which is full of challenges, perhaps signing several quality players is needed to add depth to his squad. Leverkusen could make a surprise in the Champions League like Dortmund did this season, but to become champions in this competition requires high concentration and maintaining consistent performance.
Very true, it's even possible to say until they are able to do it a second time or maintain a sane level of consistency and strength, most likely they were just lucky in the last season, Leverkusen cannot be seen as a very big team just already as there are teams out there especially in the champions league who has been able to maintain this stands with some kind of consistency and strength which makes them outstanding in the champions league, even PSG who has not been able to win the league title, they have been able to maintain a consistent appearance which some times they end up at the finals.
Experience I always say has a lot to do with a teams performance especially in the champions league because they will definitely get to a point where the only advantage you may have another team like you is the experience in the champions because even such a a team is a champion in their domestic league and that is. Why they are in the champions league at this point, teams like Madrid, Manchester city and other top team just have the advantage of the wealth of experience they have got over the others in the champions league because these teams are found in the champions league almost every year and the are able to finish beyond the group and knock out stages.