In 2004, he was considered the top pitching prospect for the New York Mets. While playing for their Double-A team, the Binghamton Mets, he was infamously traded along with minor league pitcher Joselo Diaz to the Devil Rays on July 30, 2004 for Victor Zambrano and Bartolomé Fortunato. This trade was, and still is, widely criticized by the New York media and fan base given Kazmir's subsequent success. There is also speculation that the move may have led to the demotion of then-General Manager Jim Duquette within the organization.
As was the case two years before with Jeremy Bonderman of the Detroit Tigers, Kazmir was traded to a losing team with a need to quickly develop young pitching. He started 2004 with the Single-A St. Lucie Mets, and after his trade to the Devil Rays, he received only a few starts at Double-A Montgomery. However, he was essentially expected to anchor a young Rays pitching staff from the time he arrived in Tampa Bay. He had a 2-3 record and an ERA of 5.67 in 8 appearances (7 starts) in 2004, but he was clearly making strides in his development; he struck out 11.07 batters per nine innings.
On June 22, 2006 Scott Kazmir passed Sandy Koufax and put himself in the 22nd spot in MLB history for most strikeouts by a left-handed pitcher before his 23rd birthday. He also picked up his team leading ninth victory in the process. On July 3 Kazmir threw his first career complete game shutout against the Boston Red Sox while striking out ten and giving up only two hits.
On July 2, 2006, Kazmir was elected by the players to appear in the 2006 MLB All-Star Game, his first all-star appearance. According to reports, he was flown to Pittsburgh for the game by fellow All-Star Alex Rodriguez, whose New York Yankees played at Tampa Bay in the series right before the game, in A-Rod's private jet. In the All-Star Game, Kazmir threw a perfect sixth inning, retiring Freddy Sanchez, Carlos Beltran, and Albert Pujols.
On May 14th, the Rays and Kazmir agreed on a four-year contract extension which guaranteed the lefty $28.5 million and has a maximum value of approximately $39.5 million if the team picks up his option for the 2012 season.
On May 30th, he set a team record for wins in a month, with 5, as the Rays shutout the White Sox 2-0.
On July 6th, it was announced that Kazmir was selected to be on the American League squad for the 2008 MLB All-Star Game.
On the morning of July 16th, Kazmir earned the win for the American League in the 2008 All-Star Game.