The positive test for the performance-enhancing substance violates the terms of the Minor League Drug Prevention and Treatment Program. Major League Baseball announced the suspension on Thursday.
Bourquin, the Tigers' second-round pick in the 2006 First-Year Player Draft out of Ohio State, split last season as a third and first baseman between low Class A West Michigan and Double-A Erie. The 24-year-old combined to bat .267 with 30 doubles, eight home runs and 77 RBIs in 118 games, but batted just .228 at Erie.
Bourquin wasn't expected to be added to the Tigers' 40-man roster ahead of Friday's deadline for protecting eligible players from the Rule 5 Draft, but that now becomes a moot point.
Jason Beck is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.