In 2013, Johnson was a major piece for the illinois Fighting Illini, who made it to the College World Series. Drasen posted a 3.97 ERA, 3-1 record, and 10 strikeouts in 22.2 innings pitched. As a redshirt freshman in 2012, Johnson started the final four Big Ten series finales, going 1-1 with a 6.00 era in 39 innings. He was listed as No. 25 prospect in the Class of 2010 in Illinois. He possessed an 8-2 record with a 2.07 ERA, and 78 strikeouts in 67 innings pitched as a senior. He was an Honorable Mention All-State honoree in 2010.