De Leon has risen from the 24th round of the 2013 Draft to the big leagues in little more than three years. After signing for $35,000 out of Southern, he got rocked in his introduction to pro ball, posting a 6.96 ERA in the short-season Rookie league. That spurred him to spend a lot more time working on his mechanics and his conditioning, a commitment that began to pay off in '14.
De Leon was the Rookie-level Pioneer League Pitcher of the Year that season, and he broke Clayton Kershaw's low Class A Great Lakes single-game strikeout record with 14 after a mid-August promotion.