He was a strongly built forward who stood at 193 cm and weighed 102 kg and, prior to the Coleman Medal, topped the league's goal kicking charts in 1943 (62 goals), 1944 (87) and 1945 (67).
In September 1939, playing for Melbourne Seconds against Richmond in the Seconds' Grand Final — Melbourne 22.12 (144) to Richmond 17.13 (115) — Fanning kicked 12 goals for the victors.
Fanning made his senior debut in 1940 and played in that year's Grand Final victory over the Richmond Tigers. Five years later he won the Best and Fairest award.
In Round 19, 1947 he kicked 18 goals, 1 point in a game against St Kilda which is a record for most goals in a VFL/AFL match, still standing to this day. This would ultimately be Fanning's final appearance in a VFL match. He kicked 97 goals for the 1947 season, the highest in his VFL career.
Fanning joined the Hamilton Football Club in the Western District Football League as captain-coach in 1948, after being offered three times the salary he was receiving at Melbourne. This appointment caused a split in the club and the Hamilton Imperials were founded.
Fanning held the Western District record for most goals in a game by kicking 22 against Heywood in 1949. The following year he kicked 20 goals Penshurst. Fanning kicked a Western District record of 151 goals in a season in 1952 . He finished his football career at Coleraine in 1953.