Andy Messersmith won 20 games (20-13) for the California Angels in 1971. He was traded to the Los Angeles Dodgers in 1973 and the following season, Andy Messersmith went 20-6, ERA of 2.59.
He was always among the leaders in wins during the 1970's, averaged over four K's a game with a great change up, and won Gold Gloves in 1974-75. Messersmith has the fourth lowest opponents batting average in baseball's history, .212.
He did not sign a contract with the Dodgers in December of 1975 and became baseball's first free agent. Hence the Messersmith ruling became the standard for major league players. He signed with the Atlanta Braves in time for the 1976 season and recorded a 11-11 record, which was his best until he retired in 1979.
Baseball Historian Archives Page 227