Buck pitched four years for Newberg High School, which won the Oregon state championship his senior year. At Oregon State University, the 6 ft 3 in (1.91 m), 210 pound, athlete majored in sociology. He played football in the Fall as a defensive-back and pitched for the baseball team in the Spring. After two years playing both sports, he decided to specialize in baseball. Buck pitched for the Beavers from 2004 to 2006, including pitching games in the 2006 College World Series. In 2005 he was an All-American along with Oregon State teammate, outfielder Jacoby Ellsbury. He had a key part in the 2006 championship series between Oregon State and the North Carolina Tar Heels. Buck won game three of the series after pitching just two days before in game one, sealing Oregon State's first baseball national championship. He finished his career at Oregon State as the school's leader in hit batters.
Buck was a third round pick for the Arizona Diamondbacks in the 2006 First-Year Player Draft. In June 2007, he had Tommy John surgery on his elbow. On August 11, 2008 Buck was traded from Arizona's minor league Single-A Visalia Oaks (along with Micah Owings and Wilkin Castillo) to the Cincinnati Reds for Adam Dunn and cash. In 2009 Buck battled arm injuries while holding a 2–3 record with a 4.91 ERA in ten starts. He ended the 2009 season playing for the Double-A Carolina Mudcats. Buck played on the Mudcats through 2011 and after posting a 1-5 record in eight starts, he was released. Buck hasn't played in the minor leagues since 2011.
During his five seasons in the minor leagues, Buck finished with a 16-22 record in 61 starts and a 4.48 ERA. Buck also held a .244 batting average in 41 at bats, despite not having any plate appearances at Oregon State.