No McNabb showed last night that when you take away QBs options you can force him into mistakes.
McNabb is not as accurate a passer as Brady and/or Manning. He is more in the vain of Bradshaw. He can throw hard and far and can scramble out of the pocket and with the power of his upper body he can still get the ball to his receivers.
However, last night the Pats took the Eagles receivers out of their patterns and then applied pressure on McNabb, many times he scrambled out of the picket only to find his receivers were not where they were supposed to be.
When the Pats did this consistently McNabb broke down and made mistakes. The Pats did the same thing to Peyton Manning. It is how you win football games. You take away the other guy's game and force him into situations he is not familiar with and try for the turnover.
McNabb is a decent QB but he is like most in the NFL. Take his game plan away and he is in serious trouble fast.
Brady can be beat but he is hard to break down. One of the reasons is rumored to be that he has exceptional peripheral vision. It is said he can track two receivers at the same time because he can see to his sides real well.
I know from studying games that he seems to look totally in the other direction of his receiver until the last second when he finally lets it loose.