Spagnuolo said he didn't know how long Butler would be out, but that the safety would be out this week. Craig Dahl started in place of Butler earlier this season, but with rookie Darian Stewart inactive Sunday with a hamstring injury, the Rams have just Oshiomogho Atogwe and Dahl as the team's only healthy safeties.
The Rams are also getting thin at cornerback.
Starting corner Ron Bartell re-aggravated a quad contusion injury and also suffered a shoulder injury and Spagnuolo said he would be would be day to day.
The team has three other cornerbacks — Bradley Fletcher (hamstring), Justin King (hamstring) and Kevin Dockery (thigh) — dealing with injuries, leaving rookie third-rounder Jerome Murphy as the only healthy cornerback.
Spagnuolo said defensive tackles Fred Robbins (toe) and Darell Scott (ankle) suffered injuries on Sunday.
Robbins had an MRI that Spagnuolo said looked "somewhat OK," but the 33-year-old anchor was expected to also have a CT scan to determine the severity of the injury. Scott, who recently returned to action from a high ankle sprain, sprained the same ankle but it wasn't thought to be the same injury.
Defensive tackle Clifton Ryan has now missed six games with migraines.
Spagnuolo said starting middle linebacker James Laurinaitis was dealing with a knee issue, though the severity was unknown.