Hanley, Staffordshire born right winger Bob Firth began his football career with Birmingham Corporation Tramways in 1907 and played for Golders Green in 1909 before he joined Second Division Birmingham City in 1909, making his League debut at Hull City that December. He scored twice in 27 games over that season and the next, before joining non league Wellington Town in 1911. Later in the year he joined Nottingham Forest making his Forest debut in October at Burnley, and soon became a regular fixture in the Forest team, scoring 14 goals in 146 games for them both sides of the First World War, during which he served in the Royal Field Artillery, rising to the rank of Acting Sargeant and winning the Meritorious Service Medal.
In the summer of 1921 he joined Port Vale, scoring 5 times in 40 appearances in his single season at The Old Recreation Ground, and he was a member of the side which shared the North Staffordshire Infirmary Cup in 1922 before joining Southend United in the summer, where he enjoyed a single season scoring twice in 41 games before retirement, already aged 36.
Despite a successful playing career, he is perhaps most famous for his coaching career. He coached Racing de Santander from 1930 to 1932, leading Santander to second in La Liga in 1930-31, behind champions Athletic Bilbao on goal difference. They went on to finish the 1931-32 season in fourth place. Firth then swapped the Estadio El Sardinero for Real Madrid. He spent two seasons in charge at Estadio Chamartín, leading Madrid to the League title in 1932-33, before leaving them after a second place finish in 1933-34. He also led the club to two successive Campeonato Regional Centro victories. He also took Madrid to the 1933 Final of the Copa del Presidente de la República, which ended in a 2-1 defeat to Athletic Bilbao at the Estadi Olímpic Lluís Companys.