Pettitte was drafted by the Yankees organization in 1990, and he signed with them roughly a year later. After debuting in the major leagues in 1995, Pettitte finished third in voting for the American League (AL) Rookie of the Year Award. In 1996, he led the AL with 21 wins and was runner-up for the AL Cy Young Award. Two years later, he was the Yankees' Opening Day starter. Pettitte established himself as one of the "Core Four" players who contributed to the Yankees' late-1990s dynasty that produced four championships. Pettitte won the 2001 AL Championship Series Most Valuable Player (MVP) Award in helping his team win the pennant. After spending nine seasons with the Yankees—a stint in which he won at least 12 games each season—Pettitte signed with the Astros in 2004. He rejoined the Yankees in 2007 and later that season admitted to using human growth hormone to recover from an elbow injury in 2002. Pettitte's second tenure with the team lasted six seasons, interrupted by a one-year retirement in 2011, and also produced a fifth World Series championship in 2009. He retired after the 2013 season.