At Stanford he was a two sport star, playing both fullback for the football team and outfielder for the baseball team. He was good enough at football to be drafted by the Bears in the 5th Round of the 1947 NFL draft (32nd overall) but declined to play football, choosing instead to focus on baseball.
As a baseball player, Merriman threw and batted left-handed, stood 6 feet (1.8 m) tall and weighed 190 pounds (86 kg). Because of his wartime service, he was nearly 24 when he was signed by Cincinnati in 1948. He had one year of minor league experience, with the 1948 Columbia Reds of the Class A Sally League, and batted .298 before becoming a member of the Major League Reds in 1949. He was the Reds' regular center fielder that season, but he batted only .230 with limited home run power, and was a reserve outfielder for the 1950–1951 Reds before being called back into military service from the reserves as a Marine pilot.
He returned to the Majors in 1954 and batted a career-high .268 in limited service before closing out his MLB career in 1955 playing for both Chicago clubs.
In retirement, he operated an insurance business and raised and trained horses in his native California. He died at 79 in Fresno, California.
Merriman was enshrined in the Stanford Athletics Hall of Fame as a baseball player in 1954. He was also inducted in the Clovis Unified School District Hall of Fame on November 4, 2017.