"You need to establish the run early". It is the most tired cliche in football but, like all cliches, it has become so due to its inherent truth. And on Monday Night Football, the San Francisco 49ers were able to do just that. In the first quarter alone the 49ers were able to gain 66 yards on the ground, on 11 carries. The 49ers were able to gain more than half of there 113 total rush yards in just the first quarter.
While the 49ers were "only" able to gain seven points in that first quarter, the damage had already been done. The Cardinals defense already had to adjust to stop the run, giving up bodies in coverage. On San Francisco's second touchdown drive, starting with 4:27 left in the first half, the 49ers only had to run the ball once, methodically marching down the field with a bunch of short gains through the air. 17-0 San Francisco, and the Niners only gained 14 rushing yards in the second quarter.
Had the Cardinals been able to slow down the rushing attack in the first quarter, than they wouldn't have had to compensate by stacking the box, and then Alex Smith wouldn't have been able to dink and dunk his way to another touchdown late in the first half. Offensive ineptitude is a major issue, but the Cardinal's defense is supposed to be able to keep them in games. Their inability to stop the run in the 1st quarter put them in a huge hole going into half.