Northwestern has fired defensive coordinator Jim O'Neil and two other assistants following a 1-11 season that marked its worst since 1989, the school announced Tuesday.
Longtime defensive line coach Marty Long and wide receivers coach Dennis Springer are also out.
"Our entire football family is grateful for what these three men brought to our program on and off the field," coach Pat Fitzgerald said in a statement. "They recruited and developed student-athletes who will be prepared for life and make our university community proud for years to come.
"Ultimately, these difficult decisions were made with the intention of putting our team in the best position for success on gameday moving forward."
Fitzgerald hired O'Neil in early 2021 following the retirement of decorated defensive coordinator Mike Hankwitz, who had been at Northwestern since 2008. Northwestern's defense regressed significantly the past two seasons, ranking 91st nationally in points allowed and 117th in yards per rush allowed.
Long had been with Northwestern since the 2008 season and produced several top pass-rushers, but the line has struggled recently, especially at the defensive tackle position. Springer joined the staff before the 2011 season.
Northwestern recorded its third losing season in the past four after finishing under .500 during the regular season just twice between 2007 and 2018. The Wildcats won their opener against Nebraska in Dublin, Ireland, before dropping their final 11 games.