Tim Graham of the Buffalo News reports that the Bills are concerned that the recent concussion suffered by QB Kevin Kolb could be career-ending. Graham adds that the team is proceeding with this in mind. Kolb, 29, left Saturday’s preseason game after he appeared to take a hit to the back of his head. Kolb has a very serious history of concussions, so this is obviously a major concern. Buffalo has already added veteran QB Matt Leinart and trade for Lions backup Thaddeus Lewis today. First-round pick E.J. Manuel is dealing with an injury, but is expected to be back for the start of the regular season. We’ll have more as the news is available. The post Report: Bills Worried That Kevin Kolb’s Recent Concussion Could Be Career-Ending appeared first on NFL Trade Rumors -.