With Brittain departing the club in 1924, Nelson retained his place in the first team the following season. He was ever present in the First Division, playing in all 42 matches, as the club finished second to Huddersfield Town on goal average. He also played in 11 cup ties during the campaign, making more appearances for the club than any other player. In the 1925–26 season he remained prominent in the first team and scored his first goals for the club, converting penalties during victories over Burnley and Nottingham Forest in the second half of the campaign. The season culminated with Nelson and Cardiff both reaching their first FA Cup final, losing 1–0 to Sheffield United at Wembley Stadium.