Ryan Nielsen has served as a defensive coordinator on three different teams over the past three years. He will not have another DC gig in 2025, but he has landed a new opportunity in the NFL. 
Nielsen has a deal in place with the Bills, as first reported by The Athletic’s Bruce Feldman. He will be brought in as a senior defensive assistant as part of Sean McDermott‘s staff. Feldman adds Nielsen had interest from multiple teams during the 2025 hiring cycle.
The 45-year-old worked in the college ranks from 2002-16 before joining the Saints. Nielsen spent five years serving as New Orleans’ defensive line coach, earning the title of assistant head coach during the final year of that span. When Sean Payton departed, Dennis Allen was promoted to head coach in 2022; Nielsen was one of the two staffers tapped to fill the vacated role of defensive coordinator for that season.
The Saints ranked fifth in points allowed and ninth in total defense in 2022, but Nielsen found himself on the move after the campaign. He took charge of the Falcons’ defense for the 2023 campaign, but the intra-divisional swap did not produce a duplication of the Saints’ success on defense from the year prior. Arthur Smith was fired at the end of the season, and to little surprise Raheem Morris opted to make sweeping changes at the coordinator spots.
That left Nielsen in need of a new position, and he managed to land another DC gig by joining Doug Pederson in Jacksonville. Pederson made a number of changes to his defensive staff in particular last offseason in advance of a campaign in which he found himself on the hot seat. Things did not go according to plan on either side of the ball for the Jags, and Pederson’s firing has since been followed by several coaching and front office changes. New HC Liam Coen recently brought in Anthony Campanile as Jacksonville’s defensive coordinator, paving the way for Nielsen to move on.
The Bills had Leslie Frazier in place as defensive coordinator from 2017-22, but his decision to take a year off from coaching led to McDermott taking over play-calling duties for the 2023 campaign. Last offseason, McDermott promoted Bobby Babich to the role of DC; after dealing with several injuries on defense, Buffalo finished the year 11th in points allowed and 17th in total defense. Nielsen will aim to help the team take a step forward in 2025.