Exploring the "Why" of Donovan's Decline: The Offensive Line

Philadelphia Eagles Offensive Line Jon Runyan Donovan McNabb

So over the last few weeks I’ve been trying to examine how good Donovan McNabb actually is. It’s easy to bandy around “top-10 or top-12 quarterback” when you’re not citing any numbers, but the stats show otherwise. Here’s the conclusion of the last installment:

Donovan McNabb Overall Quarterback Rank Advanced Stats

The truth is, McNabb is only a little better than average compared to the rest of the league — not just last year, but over the last three years. That’s pretty clear by this graph.

The question, of course, is why? It’s easy to just say he’s getting older, and that’s true. But what has caused this plateau? Is it just McNabb? Or can we isolate some other factors?

Time to do some breakdown. (This was going to be one long post, but that wasn’t working out, so I’m splitting it up into multiple.)

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Offensive Line

Let’s start with the big uglies. After all, the first and easiest offensive excuse after last season is line play. Derek at IgglesBlog sums up that view nicely for us:

Consider too the unsettled state of the offensive line.  That thing was a mess almost the entire season.  And then once they finally did get things straightened out — albeit without their single most dominating guy — Jamaal Jackson blew out his knee and suddenly Nick Cole was snapping balls into his butt and Max Jean-Gilles was again prominently involved.

True, true, and true. But how bad was the O-line? And does a decline up front really explain the last three seasons of stagnant play from McNabb?

Philadelphia Eagles Offensive Line Adjusted Sacks Rate

I’m not sure there’s any one great metric for calculating pass blocking. But above you have Football Outsiders’ Adjusted Sack Rate (sacks + int. grounding / pass attempt, adjusted for down, distance, and opponent) for the Eagle O-Line from 2000 on.

Overall, it actually looks as though the offensive line has been improving since early in McNabb’s career (although Donovan running around back there less has to help). Even in 2009, which was a shaky year, the numbers are in line with McNabb’s prime years of 04-06. That would suggest, right off the bat, that the front five wasn’t the problem.

Philadelphia Eagles Offensive Line Adjusted Sacks Rank

But now we have to look to see how the offensive line did compared to the rest of the league and try to give some context to the numbers. Somewhat surprisingly, the Eagles have never been that great in this category. Only in 2008, with the last efforts of Tra and Runyun, did the offensive line crack the top ten — and that didn’t correspond to some grand increase in McNabb’s production. However, if you stop the analysis with 2006, there’s probably a good argument to be made that Adj. Sack Rate and McNabb’s production are very closely tied.

The problem is that over the last three years the rate has been extremely variable — yet McNabb’s production remains more or less the same compared to the rest of the NFL.

We’re looking for something that can explain the drop off from 06 to 07, and the subsequent plateau. Protection issues can’t do that for us — at least alone. There must be other, bigger factors at work.

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Make sure to stop by over the next few days. I’ll be hitting running game, wide receiver play, and more to try to find that missing link that can explain McNabb’s decline.