D.J. Fluker (concussion) did not practice. Suffered injury late during Wednesday's practice and was diagnosed afterward. — Michael Gehlken (@UTgehlken) September 19, 2013

Well, that's not good. Can't imagine the league would be cool with a player playing, especially along the offensive line (where your helmet is constantly being smashed into a defensive lineman's helmet), four days after getting a concussion. The unofficial rule that most teams have been playing by is that a diagnosed concussion means the player gets a game/week off.

DJ Fluker did not practice today. Concussion. Coaches wouldn't rule him out for Sunday, but ... #chargers — Annie Heilbrunn (@annieheilbrunn) September 19, 2013

D.J. Fluker is a very important part of the San Diego Chargers offense and their gameplan against the Tennessee Titans on Sunday. Mike Harris is the only backup offensive tackle on the roster, so he would likely get the start if Fluker can't go.

Another thing to consider here is that Fluker is a rookie, and the Chargers have a lot invested in his future. It makes sense for them to sit him out as a precautionary measure, because one game does not matter more than D.J.'s entire career.