Justin Louis "Joba" Chamberlain (/ˈdʒɒbə/ JOB-ə September 23, 1985) is an American former professional baseball relief pitcher. He played in Major League Baseball (MLB) for the New York Yankees, Detroit Tigers, Kansas City Royals and Cleveland Indians.
Chamberlain played college baseball for the Nebraska Cornhuskers before the Yankees selected him in the first round of the 2006 MLB draft. He ascended through the minor leagues and made his MLB debut in 2007 as a relief pitcher during the Yankees' pursuit of a berth in the MLB postseason. The Yankees adhered to what became known as the "Joba Rules", where they carefully monitored and limited his appearances. During the 2008 season, the Yankees transitioned Chamberlain to the starting rotation, and he suffered a shoulder injury later in the season. Chamberlain struggled as a starter in 2009, and was shifted back to a relief role. He signed as a free agent with the Tigers before the 2014 season, and re-signed with the Tigers for 2015, but was released during the season. He returned to MLB later in 2015 with Kansas City.