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Jason Gilbert Giambi (; born January 8, 1971) is an American former professional baseball first baseman and designated hitter. In his Major League Baseball (MLB) career, which began in 1995, he played for the Oakland Athletics, New York Yankees, Colorado Rockies and Cleveland Indians. Giambi was the American League MVP in 2000 while with the Athletics, and is a five-time All-Star who led the American League in walks four times, in on-base percentage three times, and in doubles and in slugging percentage once each, and won the Silver Slugger Award twice. Giambi has publicly apologized for using performance-enhancing drugs during his career.

Looking for a veteran bat to help their playoff push, the Rockies agreed to a deal with Giambi on August 23, 2009. He was assigned to their AAA affiliate, the Colorado Springs Sky Sox. Giambi chose to wear the number 23 for his jersey's number. His first RBI with the Rockies came in the form of a bases loaded walk in his first plate appearance on September 1, 2009, after being promoted to the club upon roster expansion earlier that day. That year, he had many clutch hits which kept the Rockies in contention for the National League Wild Card. He quickly became a fan favorite in Colorado.  On January 23, 2010, Giambi reached an agreement to return to the Colorado Rockies. On September 12 Giambi hit a walk-off home run against the Arizona Diamondbacks, extending the winning streak for the Rockies to 10 games.  The Colorado Rockies announced on January 17, 2011 a deal to put Giambi in the team's minor league organization with a spring training invite for the 2011 season. Giambi made the 2011 Opening Day roster out of spring training.  On May 19, 2011, against the Philadelphia Phillies, Giambi hit three home runs in one game, the first such game for him of his career. The three home runs came in his first three at-bats. Giambi is also the second oldest player to accomplish the feat; at age 41, Stan Musial was the oldest player to hit three home runs in one game on July 8, 1962.  Giambi became a free agent after the 2012 season and was a finalist for the Rockies major league managerial opening, which eventually went to Walt Weiss. Giambi was offered the position of Colorado's hitting coach but turned it down.
Jason Giambi