In a press conference this afternoon, Packers General Manager Ted Thompson indicated that outside linebacker Clay Matthews would miss "a few days" due to a hamstring injury. Thompson characterized the injury as a "tweak" but didn't seem to think it would linger or be a cause for concern going forward.
Matthews was slowed last preseason by a hamstring injury as well.
UPDATE: In his post-practice press conference, Mike McCarthy indicated Matthews would miss two weeks. He also indicated it was the same hamstring the linebacker had trouble with last year at this time.
"I firmly believe that any man’s finest hour, the greatest fulfillment of all that he holds dear, is that moment when he has worked his heart out in a good cause and lies exhausted on the field of battle – victorious."