The decision to line up Charles Woodson at safety makes no sense. It's not that Woodson can't play safety, it's that the Packers couldn't compensate for his absence at cornerback. Williams started at cornerback and was frequently left alone in man coverage, and he couldn't handle it.
On the Texans' third offensive play, wide receiver Kevin Walter ran deep down the left sideline, and Schaub underthrew him. The problem for the Packers is that Walter had already blown past Williams before Schaub had released the ball, meaning Williams had his back turned, trying to chase Walter, and didn't know the ball had been underthrown. That allowed Walter to come back to it and grab it at the 30-yard line. Packers safety Nick Collins came over to try to help but ended up colliding with Williams, giving Walter an easy stroll to the end zone.
4 hours ago