Oklahoma assistant coach Ruffin McNeill said he is leaving the program to help care for his 85-year-old father in North Carolina.
The school made the announcement in a news release on Thursday.
Oklahoma coach Lincoln Riley hired McNeill in 2017.
He coached defensive tackles that season and at the start of the 2018 season before being named interim co-defensive coordinator for the final eight games of 2018.
Riley and McNeill have coached together in some capacity for 15 of the past 17 years.
McNeill said he is not retiring and plans to return to coaching someday.