Fewell was fired after by Tom Coughlin after a disappointing 2014 season that saw the Giants defense finish 29th in the league and be victimized several times late in games. Fewell was Giants defensive coordinator for five seasons, and before that had been defensive coordinator for the Buffalo Bills for four years, also serving seven games as interim head coach.
The 49ers have a new head coach in Jim Tomsula, and have hired former New York Jets and Cleveland Browns head coach Eric Mangini as defensive coordinator.
Fewell has an extensive background as a defensive backs coach, having filled that role for the Jacksonville Jaguars, St. Louis Rams and Chicago Bears from 1998-2005. He would seem over-qualified for that responsibility now, but after his stint with the Giants it appears no one is asking him to run a defense. A position coach job would simply be a way for Fewell to stay in the league.