After the Nationals selected Nathan Karns in the twelfth round of the 2009 MLB draft, some post-selection analysis suggested that Karns had a few good pitches, but poor mechanics would likely cap his potential. During the 2011 and 2012 seasons, Karns' performance began to prove draft skeptics wrong. In an extended stay in high-A in 2012, he posted a 2.26 ERA and struck out nearly 11 batters per nine innings. He debuted in the major leagues in 2013, and was traded to the Rays during the following offseason.
In the minors, Karns relied on a 93 mph fastball and a devastating curveball.