Hansi Flick will have difficulty to improve Barcelona defense if he wants to gain success with Barcelona. If he fails to improve defense system for Barcelona, there is very small chance of success there. Furthermore, attacking power of Barcelona was affected a lot last season with decreasing performance of Lewandowski because of ageing. Ageing effect on Robert Lewandowski can become bigger in a new season and this bring another big difficulty to Hansi Flick.
For Hansi Flick to accept the offer of becoming Barcelona coach, I believe he is ready to face the challenge brought before him about the financial downgrading of the Barcelona team to sign new quality players, to make use of the currently available players to win matches and to top the laliga league table but not to win the trophy.
I think Hamsi Flick has a big task ahead of him to fix in Barcelona, to keep the players fit and give them the courage that they can get to the top of the table once again with Him not with Xavi, despite the change of new manager with new football tactics and new players signed