Sanborn (groin) was placed on the injured reserve list Monday.
Sanborn had already been ruled out for Monday night's matchup against the Cardinals, but he'll now be forced to miss Dallas' next four games after being placed on IR. The Wisconsin product appeared in six games prior to injury, recording 34 total tackles and one pass defended. Expect Shemar James to operate as the Cowboys' top middle linebacker while Sanborn is sidelined.