St. Brown sustained a concussion during Sunday's game at Dallas.
Per Dave Birkett of the Detroit Free Press, St. Brown appeared to stumble toward the sideline after taking a hit on the Lions' second possession of the contest. The nearest referee sent St. Brown to the sideline, and after a visit to the blue medical tent, the wide receiver went to the locker room without a helmet, at which point a concussion was confirmed. St. Brown -- who won't return to Sunday's game -- thus will be subject to the protocol for head injuries before he'll be able to return to action.