A hard throwing right-hander, he initially signed with the Boston Red Sox, making his major league debut in 1984. In 1986 his 24 wins helped guide the Sox to the World Series (which they lost) and earned Clemens the Most Valuable Player award for the regular season and the first of his 6 Cy Young Awards. Clemens also won the award in 1987, 1991, 1997, 1998 and 2001. In 2001 he became the first pitcher to win 6 Cy Young Awards, and he also became the first player to win either the MVP or Cy Young Award with three different teams.
Clemens signed with the Toronto Blue Jays in 1997. In both seasons for which he pitched for the Blue Jays, he won the Cy Young Award. Then, to the disgust of many Boston fans, Clemens joined the New York Yankees as a free agent in 1999. In 2001, he won 20 games while losing only 3, at the age of 39.
Clemens attributes his longevity to a grueling fitness regimen.