Kelly, 26, is ranked by MLBPipeline.com as the Padres' 30th-best prospect and was a key component in the 2010 five-player trade between the Boston Red Sox and the Padres that featured three of Boston's top prospects in Kelly, Anthony Rizzo and Reymond Fuentes (and a player to be named later) being sent to San Diego in exchange for Adrian Gonzalez.
He spent the majority of the 2015 season between the San Diego Padres' Triple-A and Double-A affiliates, making a combined 31 appearances, including 17 starts. He posted a 3.13 ERA through his first 15 appearances (one start) of the season and finished the year with a 2-10 record and a 5.