Casillas (neck) is active for Sunday's game against the 49ers.
The Giants had already ruled out three linebackers (Keenan Robinson, B.J. Goodson and Devon Kennard) due to injury earlier this week, so Casillas' return from a three-game absence comes at a fortunate time. Despite seeing hefty snap counts in his first five appearances of the season, Casillas only managed 19 tackles and no turnovers, limiting his IDP utility as a result.