"I'm very thankful for the opportunities the Tigers provided me and looking forward to joining the A's," Smith said. "I have heard nothing but great things about the coaching staff and the organization as a whole. I'm truly excited to be going home to the West Coast."
Smith made his major league debut last season in June and made 10 appearances before being sent back to the minors. The 2011 17th-round selection of the Tigers compiled a 5.40 earned-run average in 11 2/3 innings. He had a 2.68 ERA in 164 2/3 innings spanning three minor league seasons.
At USC, the right-hander made 60 appearances with a 3.77 ERA over three years before having Tommy John surgery after rupturing his ulnar collateral ligament.