Brown (concussion) did not participate in Tuesday's practice. Brown played every single offensive snap during the Patriots' 24-21 loss to the Bills this past Sunday and wasn't diagnosed with a concussion until after the game. He'll have to clear the league's five-step concussion protocols in order to play against the Chargers on Sunday. If Brown isn't cleared, Cole Strange (knee) would be the next man up to start at center for New England.