Eric Washington
Eric Washington has been with the Buffalo Bills since 2020 when he was hired as defensive line coach and has been in that role for the past three years. However, Sean McDermott worked extensively with Washington prior to that from 2011 to 2016 when both were with the Carolina Panthers.
During that stretch, McDermott was the defensive coordinator while Washington was the defensive line coach. After McDermott left to take the head coach job with the Buffalo Bills, Washington was promoted to replace him as defensive coordinator and spent two years in that role.
He seems like the most likely candidate to replace Leslie Frazier as he knows this defense well from the number of years working with McDermott and also has experience calling plays from his time in Carolina.