The injury Kolb suffered Sunday had less to do with durability than bad luck.
The San Francisco 49ers' Justin Smith beat Cardinals guard Daryn Colledge with a power move to sack Kolb and force a fumble. As Kolb fell to the ground, his head dropped into Ahmad Brooks' path. Brooks' lower leg struck Kolb in the head as Brooks ran after the football.
John Skelton is playing quarterback for the Cardinals. Kolb has returned to the sideline after leaving for tests. It's unclear whether Kolb will return.