Miller suffered an unspecified injury that left him motionless on the field for nearly 10 minutes, according to the Cleveland Plain Dealer. Miller was eventually immobilized on a board, carted to an ambulance and then taken to a local hospital. It's not clear if Miller collapsed or was injured.
Browns coach Rob Chudinski told the Associated Press it was a head injury.
The team later tweeted that Miller is doing okay and that he's awake, alert and moving all four extremities.
Before Miller was taken to the hospital, media members on-site described a somber scene.
An unidentified #Browns player has been down on ground for 5 minutes. Practice has stopped. Players kneeling. Complete silence. Scary scene— Nate Ulrich (@NateUlrichABJ) July 27, 2013
Extremely eerie scene at #Browns practice. Music off. No one speaking. Most players on a knee. Player is down, not identified.— Ryan Lewis (@RyanLewisABJ) July 27, 2013
The injury appeared to be so serious at one point, that the media was asked not to identify the player until the family could be notified of the injury.
#browns player carted to ambulance. team has asked not to identify until family notified.— Mary Kay Cabot (@MaryKayCabot) July 27, 2013
Miller was a fifth-round draft pick of the Browns out of Colorado in 2012. The 24-year-old saw action in eight games for Cleveland as a rookie last season.