During the final moments of practice on Monday, Bengals defensive end Carlos Dunlap "walked off the field with trainer Paul Sparling" with an injury that didn't "look to be serious." According to ESPN NFL Insider Adam Schefter, Dunlap suffered a concussion and that "he is out for now."

Bengals DE Carlos Dunlap is not practicing right now due to a concussion he suffered earlier in the week. He is out for now. — Adam Schefter (@AdamSchefter) July 31, 2013

Despite securing a five-year extension several weeks ago, securing the defensive end in a Bengals uniform through 2018, Dunlap has had a history with injuries that's prevented him from playing a full 16-game season during any of his three seasons.

Lewis confirmed the injury after Wednesday's practice, calling it a "mild concussion" with an unknown time frame for his eventual return.

Figure that the team wants to keep Dunlap completely sidelined until the issue is completely resolved and the medical staff (and maybe an independent staff) clears Dunlap for contact, which may take a while. At the very least, the preseason opener against Atlanta is extremely doubtful.