Per Marvez, Wannstedt will have the titles of Assistant Head Coach and Linebackers Coach.
Wannstedt was in Cleveland to interview for the Browns' vacant defensive coordinator position on Thursday, but is now apparently out of the running there. (This could be an indication that former Bills head coach Dick Jauron will soon be named to that very post, as an aside.)
Gailey and Wannstedt coached together for two years in Miami, where Gailey served as Wannstedt's offensive coordinator. Wannstedt will at least replace DeMontie Cross as inside linebackers coach; Cross was released from that role after the regular season concluded. It's unclear if Wannstedt's title has any effect on current outside linebackers coach, who was a holdover from Jauron's staff the previous year.
More to come on this front, but revel in the fact that the Bills have added a smart, experienced coach to the defensive side of the football.