Xabi Alonso is great coach and a lot of persons still doubt it. Coaching a big club like Real Madrid comes with alot of pressure and responsibility and besides leading a big club like Real Madrid to winning the LaLiga trophy isn't a small tasks. Yes Xabi Alonso is man to the task,I believe in his capacity to outpace Real Madrid major Rivals Barcelona for the LaLiga title in the coming season.
Xabi Alonso is a great coach, no one will contradict with this. But Alonso has never taken charge of a big club like Madrid before. He was successful with Leverkusen. The scenarios of Leverkusen and Madrid are completely different. Leverkusen's target was only to secure the Bundesliga title. But Madrid's target is not only to win the La Liga title. Madrid also wants to secure the Champions league and the Copa del Rey title. And it is quite difficult to maintain a good performance consistently in such a busy schedule.
As well , Madrid has a lot of star players in the squad. And controlling so many star players is not an easy task. Even then, since Xabi Alonso is talented, it is expected that he will be able to do this difficult task comfortably.