At 16 years of age, Merrett was rejected by Richmond legend Jack Dyer because of his light frame, but he was given another opportunity at Victoria Park, where he stood out in a set of practice games for Collingwood just before the 1950 season.

In 1952, Merrett came equal sixth in the Brownlow Medal, and won a top three finish in the Copeland Trophy.

A year later he again finished in the top 10 in the Brownlow Medal and celebrated the 1953 premiership with the Magpies, when he was one of the best players in the Grand Final.

In years that followed, Merrett performed consistently and he continued to be regarded as one of the best kicks in the league, as well as one of the best wingmen.

In 1997, he was included in the Collingwood Football Club Hall of Fame and Team of the Century, on the wing.