Answer
The answer to the question is the semi-finals. Dier's first goal for Tottenham Hotspur came in a 2-0 victory over Sheffield United in the first leg of the semi-finals of the 2014–15 Football League Cup. The match was played at White Hart Lane on 21 January 2015. Dier scored the opening goal of the match in the 31st minute with a header from a corner kick taken by Christian Eriksen.