Buffalo Bills quarterback Kevin Kolb suffered a concussion in Saturday's preseason loss to the Washington Redskins a league source told ESPN NFL Insider Adam Schefter. Per the source the Bills are proceeding as if the concussion which was termed "serious" could be career-ending. Kolb will undergo a battery of tests and the Bills do not want to rush him back even if he can continue his career the source told Schefter. While diving for a first down in Saturday's game Kolb was kneed in the helmet by a Redskins defender. He remained on the field for the final four plays of the drive before departing for the locker room with what the team called concussion-like symptoms. Kolb who turned 29 on Saturday missed time in 2010 and 2012 with concussions a history that has the Bills concerned. The Bills are already without rookie EJ Manuel who underwent a minor procedure on his left knee last week. On Sunday the Bills signed veteran quarterback Matt Leinart and traded with the Detroit Lions for backup quarterback Thad Lewis.