Mackerras was drafted by the Commerce Park Gladiators in 1933, being taken 2nd in the third round and being drafted 34th overall. Mackerras would sign an extension with the Gladiators in 1940 before leaving Commerce Park to sign as a free agent with South Zealand. In 1943, he would begin his long and storied run with Wanganui, a team he played with until his release in 1954. Mackerras would sign with Sydney for ƒ72,000 per year. Mackerras would finish his career with the North Lambton Athletics before his unconditional release and retirement in 1958.