 Immediately after agreeing to terms on June 16, 2004, Happ was assigned to the Batavia Muckdogs of the Short-season A-level New York–Penn League, where he posted a 2.02 ERA in eleven starts, averaging more than one strikeout per inning pitched.Happ again impressed in 2005 with the low-A Lakewood BlueClaws.While Happ played for only half of the season, he compiled a 2.36 ERA in 72⅓ innings.