ステート・カレッジ・スパイクス
Irwin was drafted by the Pittsburgh Pirates in the 21st Round of the 2009 Major League Baseball draft. In 2009, Irwin pitched for the State College Spikes. In 2010, he pitched for the West Virginia Power. In 2011, he pitched for the Bradenton Marauders and the Altoona Curve. In 2012, he pitched for Bradenton, Altoona and the Indianapolis Indians. In November 2012, Irwin was added to the 40-man roster to protect him from the Rule 5 draft.