Fisher broke his leg in preseason practice in 2010 and missed the entire season. He could have asked the NCAA for eligibility in 2013.
Fisher said Monday it's "time to move on" and put all his energy into preparing for medical school. He said he appreciated the time coach Bo Pelini gave him to finalize his decision.
Fisher started five of 14 games this past season, and his 48 tackles ranked ninth on the team. He carries a perfect 4.0 grade-point average in business administration/pre-medicine.