A hard throwing right-hander who grew up in the Houston area, 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 six Cy Young Awards. Clemens also won the award in 1987, 1991, 1997, 1998 and 2001. In 2001 he became the first pitcher to win six 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 was traded to the New York Yankees before the 1999 season for David Wells, Homer Bush and Graeme Lloyd. In 2001, he won 20 games while losing only 3, at the age of 39.
Early in 2003, he originally announced his retirement, effective at the end of that season. On June 13, 2003, pitching against the St. Louis Cardinals in Yankee Stadium, Clemens, at age 40, recorded his 300th career win and 4,000th career strikeout, the first player in the history of baseball to record both milestones in the same game. The 300th win came on Clemens' fourth try; the Yankee bullpen blew his chance of a win in his previous two attempts. Clemens became the 21st pitcher ever to record 300 wins and just the third ever to record 4,000 strikeouts, joining Nolan Ryan (5,714) and Steve Carlton (4,136). His career record upon reaching the milestones was an impressive 300-155; his record at the end of the season was 310-160 with 4,099 strikeouts.
He chose to put off his retirement, signing a one-year deal with his hometown team, the Houston Astros, for the 2004 season. He will join his close friend and former Yankees teammate Andy Pettitte in the Astros' starting rotation.
Clemens attributes his longevity to a grueling fitness regimen.