David Shelley Duncan (born September 29, 1979 in Tucson, Arizona) is a Major League Baseball first baseman, outfielder, and designated hitter for the Cleveland Indians.
Duncan is the oldest son of Dave Duncan, a MLB catcher and pitching coach. His younger brother, Chris, is also a MLB first baseman and outfielder.
Shelley graduated from Canyon del Oro High School, located in the Tucson suburb of Oro Valley, in 1998. While there he was a teammate of current All Star second baseman Ian Kinsler. He played on the school's 1997 baseball team that went on to capture the 5A State Championship title.