Pelini returned to the Tigers' coaching staff in 2020 and had previously been the school's defensive coordinator from 2005-07.
LSU defensive coordinator Bo Pelini is not expected to return in 2021, according to Sports Illustrated's Ross Dellenger.
Alabama.com's Matt Zenitz first reported news of Pelini's expected exit.
Pelini returned to the Tigers' coaching staff in 2020 after serving as the head coach at Youngstown State for the last five seasons
This year, the Tigers' defense is ranked second-to-last in the SEC in total defense, second-to-last in pass defense and is fourth-worst in yards per carry allowed.
Pelini replaced Dave Aranda, who left the school last offseason to become Baylor's head coach.
The 53-year-old Pelini had also previously been the head coach for seven seasons at Nebraska as well as LSU's defensive coordinator from 2005-07. In his first stint as defensive coordinator with the Tigers, LSU’s defense ranked No. 3 nationally in total defense all three years.
According to Sports Illustrated, defensive line coach Bill Johnson is expected to retire and safeties coach Bill Busch is not expected to return to the staff.
LSU finished the 2020 season 5-5, and notified the NCAA and SEC in early December that it was self-imposing a "one-year postseason ban on its football program for the 2020-21 bowl season" after reviewing rule violations discovered during an NCAA and IARP investigation.