harrison played football, baseball and basketball at lee's summit west high school in lee's summit, missouri. in football, he had 60 receptions for 1,007 receiving yards, 13 receiving touchdowns, 198 rushing yards, 12 rushing touchdowns and threw a touchdown pass as a senior. he committed to the university of nebraska to play football in july 2013. he was considered one of the top prospects for the 2014 major league baseball draft and was also one of the top college football recruits. he was ranked as a four-star recruit by rivals.com, and was their 33rd best wide receiver in the class. prior to the mlb draft, he was undecided if he was going to attend nebraska or play professional baseball.