Devitt's first forays into national competition were at the 1952 Australian Championships, where he was continually in the shadow of club-mate Barry Darke, who set five Australian records in their age group. Devitt trailed Darke again at the 1953 championships, but Darke retired afterwards to become a mechanic, leaving Devitt to dominate his age group. However, in the open ranks, he was often beaten by Jon Henricks in the sprint events, and Gary Chapman and Murray Rose in the longer events. Rose and Henricks went on to claim individual gold at the 1956 Summer Olympics. At the age of 18, with Henricks initially sidelined by injury, Devitt was named as the captain of the New South Wales team for the 1955 Australian Championships. However, Henricks recovered and relegated Devitt to silver in the 110-yard freestyle. He claimed silver in the 220-yard freestyle, behind Rose. Devitt's decision to concentrate on sprinting led to conflict with Penny, and he then left Penny and began self-coaching. After beginning to regress, Devitt considered retirement, until he joined Sam Herford at the Spit Baths alongside Murray Rose.