The comments to Parts I and II of this series have been great, so let me start with a thank you. One of the more difficult parts of this process is comparing players across eras not just for efficiency, but for gross volume. In 2013, teams averaged 38.0 pass attempts (including sacks) per game, compared to just 24.5 in 1956. A great quarterback will be above average in either era, but it’s easier for great quarterbacks to accumulate above-average value when they play in a high-dropback era.

So what’s the solution? Simply pro-rating the numbers feels a bit too dramatic; we got into a similar issue with True Receiving Yards, and our solution there was to take a (literal) middle ground approach. I thought it would be fun to apply the same philosophy here. Over the course of the 96 league seasons in this study, the average number of league-wide dropbacks per game was 26.1. If we were going to do a 1:1 adjustment, we would then multiply each quarterback’s value in 2013 by 0.687, since that’s the result of 26.1 divided by 38. Instead, I decided to split the baby, and take the average of 0.687 and 1.000, which means modifying the VALUE metric for each quarterback in 2013 by 84.4%. On the other hand, a quarterback in 1956 now gets his VALUE multiplied by 103%, and a passer in 1937 sees his score multiplied by 129.0%.

The table below shows the revised single-season leader list. Here’s how to read it, which will explain why Dan Marino climbs back ahead of Tom Brady into the top spot on the list. Under the old system, Marino had a value of 2,267 yards above average, but with the modifier, he gets downgraded to an adjusted value of 1981; of course, Brady’s modifier is more severe, which is why Marino vaults him. Meanwhile, thanks to a 110.3% modifier, Sid Luckman’s 1943 season jumps ahead of Peyton Manning’s 2004 season, which has a modifier of 88.1%. The table below shows the top 200 single seasons using this formula.

But let’s move on to the fun stuff: the career list, using the same 100/95/90 formula. The table below shows where each quarterback ranked in Part II (the Old Value and Old Rk columns), along with where they rank using this adjusted dropbacks modifier (the New Val and New Rk columns). I also included two other columns: using this new formula, I eliminated all seasons where a quarterback had below-average value. So the New Val+ and Rk+ show how each quarterback fares when you only look at their positive (i.e., above-average) seasons.

Some thoughts:

Obviously the quarterbacks most harmed by this adjustment will be modern quarterbacks, but there’s not that much movement at the top. Manning, Brady, Drew Brees, and Aaron Rodgers all see their values drop by at least 250, but that doesn’t mean too much. Perhaps a more significant modifier is necessary? Then again, are Brees and Rodgers already too low at 9 and 19, respectively? One might quibble with Brees’ stats because of dome effects, but that should be handled outside of era adjustments, in my opinion.

Also not surprising, older quarterbacks are the biggest beneficiaries here. Luckman moves from 19 to 13, Sammy Baugh from 18 to 14, Arnie Herber from 54 to 33, Cecil Isbell from 40 to 30. Otto Graham jumps from 13 to 11, while Johnny Unitas moves from #8 to #6.

What if we eliminate all negative seasons? Ken Stabler moves up significantly. You probably didn’t even notice it (and if you did, you didn’t comment about it), but the Snake ranked just 66th in Part II. After adjusting for dropbacks, he only moved up to 64th, but by removing negative years, he jumps up to #45. I’m sure fans of a certain age (or certain part of the Bay area) would be incredulous at such a low ranking for Stabler. But Stabler was about as bad as you can be from 1980 to 1984: he ranked 41st out of 43 quarterbacks in ANY/A over that period, and had significantly more attempts than the two passers below him. In the ’70s, Stabler had a career ANY/A average of 5.23, which was pretty good; his work in the ’80s dropped his career ANY/A to 4.74, despite rising league averages during that time. A 45th-place ranking is much more representative of Stabler’s career; combined with his great postseason (see below), and there’s enough there for Raiders fans to be annoyed that the Snake isn’t in the Hall. Of course, Lamonica gets my vote as best Raiders quarterback of all time.

Milt Plum, Boomer Esiason, Joe Ferguson, Matt Hasselbeck, and Neil Lomax also make pretty decent jumps if you remove all negative seasons. I leave it to the reader as to whether that’s appropriate. Let me know your thoughts in the comments.

Troy Aikman falls from 40th overall to 33rd once you remove negative seasons. In his middle nine seasons, Aikman averaged 6.19 ANY/A. But in his first, second, and final seasons, he produced an ANY/A between 3.0 and 4.0 each year, and had between 250 and 400 attempts. As a result, his career ANY/A is “just” 5.66. When we think of Aikman, we tend to think of Troy Aikman, not the guy who was miserable in his first, second, or final years, so a 33rd place ranking (as may be boosted by his playoff production) is probably more appropriate.

Of course, for some, putting Aikman 33rd is still too low. We’ll get to the playoffs in a moment, but let’s look at Aikman’s regular season numbers. We all know his gross numbers are not impressive, but a run-heavy offense shouldn’t have harmed Aikman’s efficiency numbers. And for the eight-year period from 1991 to 1998, Aikman posted an excellent ANY/A of 6.25, which gave him an ANY/A+ index of 114. In ANY/A+, a quarterback gets credit for his standard deviations above average, with one standard deviation being equal to 15 points, and average being equal to 100. So Aikman was essentially one full standard deviation above average during that period. Which is really, really good. He may not have posted outstanding gross numbers, but he was very efficient. Of course, over the last eight years, Tony Romo has had an ANY/A of 6.96 and an ANY/A+ of 115.

Of course, the real “issue” with Aikman isn’t his efficiency numbers, but that his playoff performances were outstanding, which are ignored by the above analysis. So let’s take a look at the postseason.

Playoffs

I’ve done a couple of quantitative studies about quarterback play in the postseason. Joe Montana has been, quite clearly, the most productive postseason passer in NFL history.

After him, Terry Bradshaw, Kurt Warner, Peyton Manning, and Aikman probably round out the top five of best postseason quarterbacks. The next tier would be a big one, and would include Brett Favre, Steve Young, Stabler, Drew Brees, Bart Starr, Jim Plunkett, John Elway, and Tom Brady. Quarterbacks like Daryle Lamonica, Aaron Rodgers, Mark Rypien, Roger Staubach, Dan Marino, Ken Anderson, Len Dawson, and Phil Simms aren’t too far behind, either.

Bradshaw, Warner, Aikman, Stabler, and Plunkett are probably the ones most investigating. Bradshaw ranks just 54th in my formula of the best regular season quarterbacks, but the 54th best regular season quarterback + the 2nd best playoff quarterback is enough to get you to the Hall of Fame. And while Bradshaw’s numbers look bad now, they aren’t nearly as bad as they seem.

Warner’s numbers look great, but he doesn’t fare all that well in this formula. There are a couple of reasons for that. He faced one of the easiest schedules of any quarterback (average of -.21), so his raw numbers are overstated (and that’s before you get to the dome/supporting cast argument). He also rarely played full seasons, which limited his ability to produce significant value. Only two of his seasons cracked the top 150, and Warner also didn’t have many “good” seasons, as he tended to either be very good or average (or worse). His incredible playoff numbers means he’ll make it to Canton, and that’s probably appropriate, but I think he tends to be overrated by many analysts.

Aikman is like a softcore version of Bradshaw. He’s not as extreme as Bradshaw, but he fits the “outstanding playoff numbers, just okay regular season numbers” paradigm. He’s a worthy Hall of Famer — at least, statistically — because he’s got good enough regular season stats and then superlative playoff numbers. But figuring out how to compare him to Romo to Staubach is too tall a task for a summer Friday.

Finally, we get a pair of Raiders quarterbacks. Both were great in the playoffs, and combined to win three titles. Plunkett is mostly a non-starter when we take about all-time great quarterbacks: Plunkett has just three seasons (’74, ’86, ’77) where he produced more than 100 yards of value above average, and zero where he had more than 350 yards. Jeff Hostetler was a better quarterback if you want to really focus on mediocre quarterbacks (who played for the Raiders!) who won a Super Bowl. As for Stabler, he lags behind Aikman in the regular season and Aikman and Bradshaw in the playoffs. Not every quarterback with great playoff numbers gets to make the Hall of Fame, but it just so happens that three of the best (including Lamonica) were Raiders. Stabler was better than someone like Mark Rypien, but there’s a pretty big gulf between players like Rypien and the Hall of Fame. Perhaps Raiders fans will feel less bothered when Eli Manning doesn’t make the Hall of Fame (right now, Manning’s argument is terrible; ignoring the “will he” question, he’s a “not even close” on the “should he” question).

As for the top of the list? It’s pretty clear to me that Peyton Manning‘s the greatest quarterback of all time. If you don’t agree with that, well, there’s probably nothing I can say to convince you otherwise.