Johnson, a rookie out of Maryland who became Detroit's starting back after Kerryon Johnson went on injured reserve last month, suffered the concussion last week against the Chicago Bears.
He practiced Thursday and Friday and was initially listed as questionable.
Johnson has 44 carries for 153 yards this season along with 13 receptions for 58 yards. He will be part of a backfield committee, along with J.D. McKissic and Bo Scarbrough, behind quarterback Jeff Driskel, who gets his second start of the season in place of the injured Matthew Stafford against the Cowboys.
Paul Perkins was expected to be part of that backfield committee, but he was released Saturday and replaced on the active roster by Scarbrough, who was brought up from the practice squad.
Scarbrough should get some work against Dallas. At 6-foot-1, 235 pounds, he's a bigger back than Johnson or McKissic and could be a short-yardage option.
His size also gives Detroit insurance in case fullback Nick Bawden, who was added to the injury report with a foot ailment and is listed as questionable, can't play.