Alonso played his first match with Sunderland on 7 January 2014, featuring the full 90 minutes in a 2–1 home win over Manchester United for the League Cup semi-final first leg and being given the man of the match award by Sky Sports. He played in the final of the competition on 2 March, not being able to prevent a 3–1 loss against Manchester City; he contributed with 20 appearances all competitions comprised, helping his team retain their top flight status.