The Lions have a 3-0 lead on the Cowboys, but they lost their No. 1 receiver for the day.
Amon-Ra St. Brown took an arm club to the back of the helmet from Cowboys linebacker Anthony Barr on a 4-yard reception in the first quarter.
He went into the medical tent for evaluation of a head injury before being escorted to the locker room.
The Lions quickly ruled him out with a concussion.
In five games this season, including Sunday, St. Brown has 28 receptions for 275 yards and three touchdowns.
Cowboys tight end Dalton Schultz went down awkwardly after a 15-yard gain late in the first half with his leg bending underneath him. He stayed down for an extended time before jogging off.
The Cowboys have four tight ends active today with rookies Jake Ferguson and Peyton Hendershot and Sean McKeon a practice squad activation.