There is no doubt that Xabi will face big problems. But since he is talented, he will definitely find a suitable way out of the problem. We can trust Alonso.
I think the question would be whether the fans or the board have enough patience for him. You also need to define the bottom line because I doubt their fans would accept if Madrid finishes outside the UCL zone, for example. It would be amazing if he successfully solves nearly everything in his first season, even though that seems like an unfair target for him.