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Crunching The Numbers: Under Further Review (Part IV of IV)

In the conclusion of my quest, I answer the question you have probably been asking since the beginning: "Of the statistics that correlate with winning, which ones did the Eagles do well?" Ask, and you shall receive. Read on below for the answer.

Howard Smith-USA TODAY Sports

It all ends here. It started with Part I, where I casually made some observations about my ranking formula. In Part II, I introduced linear regression analysis and found out which of the metrics I was using correlated with winning and which ones didn't. After making some surprising discoveries, I made a compilation of the statistics that do correlate with winning in Part III. And now, to conclude this series, I took these "critical metrics" and looked up how the Eagles ranked to see what they did well and where they could improve. Like before, we'll start with the offense.


[Note: the metrics are listed in order of their correlation to winning. For the specific r-values, see Part III.]

Statistic Rank
Points Scored/Game 6
Fourth Quarter Scoring 7
Third Quarter Scoring 3
Second Quarter Scoring 12
Third Down Efficiency 14

It's no surprise that the Eagles fared very well in the scoring statistics. Their third-down offense could use some improvement, however. Some of the cause for this might be because the offense often took time getting into a rhythm and started off games with three-and-outs. Since the majority of the starters will now be more comfortable with the system, it's not unreasonable to speculate that they will hit their stride faster this season and increase their ability to convert third downs. What does the offense look like broken down into its components?

Statistic Rank
Rushing First Downs/Game 1
Rushing Play % 6
Rushing Attempts/Game 5

Rushing first downs had the biggest correlation with winning in the run game, and the Eagles had more of them than any other team in the league last season. Predictably, they also did very well in the other two metrics in Kelly's run-first system. If the defense can mature more in Year 2 under Bill Davis, they might be able to force punts sooner and have more opportunities to run the ball.

Statistic Rank
Average Passer Rating 3
Yards/Pass Attempt 2
Incompletions/Game 5
Yards/Completion 1
Passing Play % 5
Completion Percentage 13
QB Sacked/Game 23

Nick Foles had a historic year in 2013 and this is reflected in the majority of the critical passing metrics listed above. An important thing to keep in mind is that they are ranked fifth in passing play percentage because they threw the ball the fifth least of any team (remember that there was a negative correlation with passing frequency). They are also ranked third in passer rating because Michael Vick's and Matt Barkley's statistics are being taken into account. Other than that, there isn't a lot of new information here - Foles did go through periods of inconsistency (however brief) and did take too many sacks. Overall, these numbers reflect a highly impressive offense, but we unfortunately can't say the same for the other side of the ball.


First, a look at the defense as a group:

Statistic Rank
Points Allowed/Game 19
Second Quarter Scoring 9
Fourth Quarter Scoring 24
First Quarter Scoring 6
Third Quarter Scoring 29

At an initial glance the rankings seem to be all over the place. Upon closer inspection, it becomes more obvious that this is a pretty good picture of the 2013 Eagles' defense. In the middle of the season, they would routinely stifle opposing offenses in the first half (evidence here by the ninth and sixth second and first quarter scoring, respectively). Then, as the defense got tired in the second half teams would come storming back, which made for some close games down the stretch of the season. They were very middle-of-the-pack in scoring defense overall but with the new system I think we can all agree they exceeded expectations. Now let's break down each unit of the defense.

Statistic (Opponents) Rank
Rushing Play % 8
Rushing Attempts/Game 22

There are only two statistics that strongly correlated with winning. The Eagles split performance in both of them, but the explanation is very straightforward. The defense fared well in rushing play percentage because teams found they could easily pass the ball against them  (remember, lower rushing attempts is better). They didn't do as well in rushing attempts purely because they were on the field more than other NFL defenses. Whether or not the Eagles can improve upon this is arguable based upon the way the offense operates. According to the trend, the defense will want their opponents to attempt more passes while preventing efficient quarterback play. At the same time, the offense's lightning pace does not really fit well with a defense that is pitching three and outs. It will be interesting to see how the evolution of their systems continues in year two. How did the passing defense compare?

Statistic (Opponents) Rank
Average Passer Rating 14
Passing Play % 7
QB Sacked/Game 20
Incompletions/Game 3
Yards/Pass Attempt 21

More mixed-bag results. Their high ranking in passing play percentage should not come as a surprise since they gave up so many passing yards last season. Interestingly, they also fared well in incompletions per game. It's possible (and maybe even likely) that this is because teams passed more, so they had more incompletions. But it's also fun to consider that the team could have been decent at forcing incompletions; with a polished corner like Fletcher, a ball hawk like Boykin, and a physical presence like Williams, it's not hard to imagine. Ultimately, more research would need to be done in order to make a real conclusion. As for the other metrics, we all know that the pass rush was lacking and that they gave up mediocre yards per attempt. The pass defense was shoddy at best. Where the defense truly excelled was in turnovers.


Here is how both sides of the ball fared with giveaways and takeaways:

Statistic Rank
Turnover Margin/Game 3
Interceptions/Game 3
Giveaways/Game 4
Interception % 4
Takeaways/Game 3
Statistic (Opponents) Rank
Interceptions/Game 6
Interception % 13

Billy Davis did a good job turning the defense into a turnover machine, as his unit didn't finish lower than fourth in interception percentage and giveaways per game. The offense also did its part in fueling the third-best turnover differential by being fourth in giveaways and sixth in interception percentage (lower is better with that metric). The only real room for improvement is interception percentage, but this number is likely weighed down by Barkley's and Vick's performances. That being said, the more likely scenario here is some regression to the mean, especially since turnovers have more to do with luck than other statistics (relatively speaking). Still, being adept at taking the ball away and being disciplined enough to protect it are very coachable skills, so it seems like the team could be on the plus-side of the turnover margin for the forseeable future.


So what did we learn? Quite a lot. To clarify the takeaways that can be gathered after wading through this mass of statistics and numbers, I'll go with bullets:

  • Not all statistics are created equal. This is a pretty obvious statement, but what isn't obvious is which statistics are more important than others. It's something that I will definitely consider moving forward with my rankings.
  • The NFL is not a passing league. Any team that tries to fill the air with footballs ends up losing. Conversely, teams that ran the ball - regardless of how effective it was - won more. To be more accurate, the NFL is a league dictated by clean, efficient quarterback play and a strong commitment to the run.
  • The league might have a love affair with the offense, but the defense is still more important to winning. The gap is probably smaller now than it was a few years ago, however.
  • The Eagles did a lot of things right last year, but there is still work to be done.
I found the insight gathered on this wonderful sport we call football to be truly eye-opening. Never before would I have imagined that yards per carry is essentially meaningless or that passing the ball more is strongly connected to losing. And it was all done with a simple function in an Excel spreadsheet.

The Eagles, for their part, are most definitely heading in the right direction. What is truly exciting is that there is still upside and room to grow - even on offense. To think that an offense as explosive as Kelly's was last year has room for improvement means that Big Chip can turn the Eagles into a perennial monster in the NFC as long as he keeps doing things the right way (and there's no reason to believe yet that he won't). The rest of the decade *should* be a good one for Philadelphia.
For as successful as Kelly's offense was in year one, there is still room for improvement.

And finally, I will end with the concession: this is only one year's worth of data. I'm sure some of these trends might fade quickly, but I have a feeling the majority of them are deeply rooted into the winning methodology in the NFL. This is definitely something I'll be tracking in future seasons to see what sticks and what doesn't. I could also go back and review previous seasons, but I frankly don't have the time for it and I think it'll be more useful to see what direction the NFL is heading rather than where it has come from.

So what about you? What's your take on all of this? Did you find any of the results from the analysis surprising? Or, as Mark Twain once said, is it all just, "Lies, damned lies, and statistics"?

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