 In college, Detwiler pitched for Missouri State University of the Missouri Valley Conference.In 2006, he was a member of the All-MVC Tournament team, and he also pitched innings in two starts for the Falmouth Commodores of the Cape Cod League, accruing a 1.74 ERA, striking out 14 batters, and issuing three walks before moving on to play for Team USA.In 2007, he finished his third year with a 2.22 ERA in 14 starts and 100 strikeouts in 89 innings.