Callachan was born in Madras, India, and was a soldier's son who became Celtic's left-back back-up to international Willie McStay. He failed to breakthrough to get regular first team action in Glasgow and, after loan spells with Alloa Athletic and Beith, arrived at City in September 1927.
He made his City debut at Newcastle United in April 1928 but was still seen as back-up to the first time during his time at the club, making only three league appearances. However, despite letting him leave at the end of the 1928-29 season City re-signed him for the following season to play yet more reserve team football.
His time after Leicester saw him play in the first ever Wigan Athletic line-up, when that club was formed to play in the Cheshire League.