Summary: Replacing Wentz with Foles removes about 6.5 points of offense from the Philadelphia Eagles, turning a high flying offense into something very average.

Last night the Atlanta Falcons defeated the LA Rams. Now we’re faced with the prospect of the Falcons playing the Eagles. I have an idiosyncratic playoff model, one I treat as a hobby. It is based on static factors, the three being home field advantage, strength of schedule, and previous playoff experience. And since it values the Eagles as 0.444 and the Falcons as 1.322, the difference is -0.878 (win probability in logits). The inverse logit of -0.878 is 0.294, which is the probability of the Eagles winning, and an estimated point spread would be a 6.5 point advantage for the Falcons.

Another question that a Falcons or Eagles fan might have is how much is Carson Wentz worth as a QB, in points scored? We can use the adjusted yards per attempt stat of Pro Football Reference to estimate this, and also to estimate how much Carson Wentz is better than Foles. We have made these kinds of analyses before for Matt Ryan and Peyton Manning.

Pro Football Reference says that Carson Wentz has a AYA of 8.3 yards per attempt. Nick Foles has a AYA of 5.4. Now lets calculate the overall AYA for every pass thrown in the NFL. Stats are from Pro Football Reference.

(114870 yards + 20*741 TDs – 45*430 Ints) / 17488 Attempts
(114870 yards + 14820 TD “yards” – 19350 Int “yards”) / 117488 Attempts
110340 net yards / 17488 yards
6.31 yards per attempt to three significant digits

So about 6.3 yards per attempt. Carson Wentz is 2 yards per attempt better than the average. Nick Foles is 0.9 yards less than the average. The magic number is 2.25 which converts yards per attempt to points scored per thirty passes. So Carson, compared to Foles, is worth 2.9 * 2.25 = 6.5 points per game more than Foles, and 4.5 points more than the average NFL quarterback.

This doesn’t completely encompass Carson Wentz’s value, as according to ESPN
‘s QBR stat
, he account for 10 expected points on the ground in 13 games, so he nets about 0.8 points a game on the ground as well.

Now, back to some traditional stats. The offensive SRS assigned to Philadelphia by PFR is 7.0 with a defensive SRS of 2.5. If Carson Wentz is worth between 6.5 and 7.3 points per game, then it reduces Philadelphia’s offense to something very average, about 0.5 to -0.3. That high flying offense is almost completely transformed by the loss of their quarterback into an average offense.

Note: logits are to probabilities as logarithms are to multiplication. Rather than multiplying probabilities and using transitive rules, you just add the logits and convert back. Logarithms allow you to add logarithms of numbers rather than multiplying them.


Summary: with some calculations based on adjusted yards per attempt, Matt Ryan’s value as a passer in the 2016 season can be shown to be almost 9 points a game more than the average QB.

Mark Zinno is a host on a sports talk show, 92.9 the Game, in the 7pm ET time slot. Often booted out of the slot by Atlanta Hawks games, he nonetheless has been a dogged supporter of Matt Ryan. This isn’t new, btw. Even in years where Matt Ryan wasn’t at his best, he would doggedly argue that Matt Ryan was an elite quarterback, and said repeatedly that compared to an average NFL team, that Atlanta was blessed.

So, we’re dedicating this blog post to Mark Zinno.

It’s hard to understand the scope of what Matt Ryan has done until you look at his adjusted yards per attempt in 2016. Pro Football Reference lists it as 10.1, which is one of the highest I’ve seen, and comparable to Peyton Manning’s 2004 season, where PM’s AYA was 10.2. Looking a little further, you can see that PFR ranks this the 4th best performance in history. Aaron Rogers is in the top 4, and for some reason, so is Nick Foles.

The value in using AYA is that you can build an expected points curve that satisfies all the requirements of the AYA function, and then use the slope of that curve to relate yards to points. Don’t worry, I did that long ago, and the result is documented here. The simple take home is the magic conversion 2.25, which converts AYA from yards to “expected points generated per 30 passes”.

Then, using the 2016 annual data from Pro Football Reference, you can calculate  what the average QB did, by calculating an AYA using the overall season’s statistics.  So the formula is:

(123639 yards + 20*786 TD – 45*415 Ints)/  18295 attempts 

(123639 yards + 15720 “TD” yards – 18675 “Int” yards) / 18295 attempts

120684 yards / 18295 attempts

6.60 AYA to 3 significant digits.

Now things become simpler. Matt Ryan generated 10.1*2.25 = 22.7 points per 30 attempts, while Joe QB generated 14.8 points per 30 attempts. The difference, rounded to a whole number, suggests that Matt Ryan was worth about 8 more points in 30 attempts than the average NFL QB this season.

That doesn’t entirely encompass his per game value. Matt threw 534 attempts  this season for an average of 33.4 passes per game. So his per game value, to the nearest tenth of a point, was more like 8.8 points a game more than the average quarterback.

But if the numbers baffle you, then the simple take home is that Matt’s statistical efficiency in 2016 is comparable to the best single season Peyton Manning ever had.