Locke is in the league's concussion protocol after being injured in Sunday's 33-30 overtime loss to the Cardinals, Patrik Walker of the Cowboys' official site reports.
Locke played a season-high 68 defensive snaps against Arizona after he'd logged just 31 snaps on defense across his previous two appearances this season. Markquese Bell would be in line for more snaps if Locke is unable to play against the Colts on Sunday.