 During the summer of his freshman year in college Detwiler played for Wentzville Legion Post 323.The Washington Nationals drafted him in the first round (sixth overall) in the 2007 MLB draft, making him the highest Missouri State draft pick in history.Detwiler was the fifth pitcher taken by the Washington Nationals/Montreal Expos franchise in the first round of the draft in the last six years following Clint Everts, Chad Cordero and Bill Bray in 2002, 2003 and 2004, respectively, and Colton Willems taken in 2006.