Alonso played for Real Sociedad, making 114 appearances and scoring 9 goals, including a brief loan period at Eibar.

Alonso joined Liverpool, winning the UEFA Champions League in his first season and making 143 appearances in all competitions.

Alonso moved to Real Madrid, winning La Liga, two Copas del Rey, and another Champions League, making 158 appearances.

Alonso joined Bayern Munich, winning three Bundesliga titles and a domestic double in his second season, making 79 appearances.