It's disingenuous to say that McNabb isn't protected by a running game. For whatever reason, the Eagles choose not to run the ball. Since McNabb came on the scene, the Eagles have ranked 24, 23, 5, 25, 31, and 30 in rushing attempts, and this includes the 40-80 attempts that McNabb throws in. The Eagles are currently ranked 22 in attempts.
One might argue that the attempts are so low because the run game is ineffective, but consider that they ranked 4, 8, 8, 4, 10, 17 in yards per attempt. They are currently ranked 3 in ypa.
The Eagles running game (or lack thereof) is a by-product of their offensive philosophy. Consider that McNabb's accomplishments (statistical and otherwise) are also a by-product of the fact that virtually the entire offensive gameplan is on his shoulders.
If the Eagles had an imposing running game, McNabb would be less impressive, at least statistically. A lot of McNabb's yards and TD's are coming in place of a running game. That's just the offensive design.