I am sure Xabi Alonso can give his best even though in his first season he fails to bring Real Madrid to win the Champions League because it does take time to change the team according to the playing pattern that he expects.
He's getting acquainted with the players gradually and also has little time to train against their next debut on Wednesday playing AI Hilal. After the match it'll be easier to speculate what the future holds for the new Coach. You can't be sure if he'd not lift the champions league at first glance. Arne slot won the EPL in his first season with Liverpool, so anything can happen if Alonso's strategy proves effective he'd come out a champion.