Chicago Bears Pro Bowl defensive tackle Henry Melton, the team's franchise player, suffered a concussion against the Carolina Panthers.
He'll have to pass an NFL baseline neurological test before he can resume playing.
Wide receiver Earl Bennett is also sidelined with a concussion.
"Henry has a concussion and he'll be in a NFL concussion protocol situation right now and will be day-to-day," Bears coach Marc Trestman told reporters.
Melton made the Pro Bowl last season when he finished with six sacks and 33 tackles.
The Bears didn't get anywhere in contract talks with Melton, so he'll play this season under the franchise tag.
Follow me on Twitter: @RavensInsider
Aaron Wilson covers the Ravens for The Baltimore Sun.
MAR 11 Jerry Angelo
How NFL teams approach that integral period of time that takes place from free agency until the draft.
MAR 07 Joel Corry
Front offices and agents of soon-to-be free agents can begin discussions this weekend.
MAR 04 Jerry Angelo
At some point, even the best partnerships in the NFL will begin to dissolve.