According to the A.P., Favre did suffer a concussion from his hit that knocked him out of lastights game. With the new rules on such injuries, that means he is going to be out at least one game. At this point, it could also call into question and return this season as possibly his career.
Of course, I do say could as we all know Favre. But at this stage of his career, it might be time for hi to sit it out till the end and call it a career instead of coming back and suffering a worse injury at this point.