After playing both football and basketball his freshman year for the Trojans, Banner says he'll stick only to football for the rest of his career at USC.
An emotional Banner told FOX Sports NEXT, "It hurts because I love basketball. But this is a business choice."
Banner redshirted his freshman season on the football team and didn't see any playing time for the Trojans basketball squad this season.
The 6-foot-9 335 pound athlete thinks he could possibly have made it on the court for new basketball head coach Andy Enfield next season, but ultimately decided it's more important for him to get time on the football field.
"I have the perfect opportunity to get myself on the field [this season]," he said. "My dream is to be on the field. After that, I want to be the best player in college. Number three goal is to be in the NFL."
Going into college Banner knew being a dual sport athlete would be a challenge and eventually realized there aren't enough hours in the day to work on his skills on the field and then put up shots on the court if he wants to realize his dreams.
He says his decision was not impacted by anything said by USC head football coach Lane Kiffin or Enfield.
"No one said 'Zach this is necessary'. Coach Kiffin told me I didn't have to do this," Banner explained. "Coach [Kiffin] could tell I was upset.
"I just feel like after last year, it being my redshirt year and everything, I just feel like I'm competing for a spot this year and I need to focus a lot more and start making a business choice.
"I came to USC to be the best and I will make a lot more progression if I have enough time."
Banner is listed third on the post-spring football depth chart at right tackle.
He has four years of eligibility remaining on the Trojans football team.