Saturday, October 8, 2011

Joe's numbers, and the moral of the story

Appreciating how the Old Ones played. Or: Joe Namath in the 2000s. Part III -- by Jim Glass.

Part I explained what is going on here and why. Part II presented the statistical background behind this comparison of the 1970s and 2000s.

Namath in the 2000s

"Namath's numbers were shockingly bad. You tend to remember Namath as this seminal figure, and of course he was, and then you see those stats and just go: 'Yuck.'" -- Joe Posnanski, Sports Illustrated.

This has become a popular notion among many football fans who never saw Namath play, and who have a little knowledge of football statistics - but not enough.

"Joe Namath is in the Hall of Fame because of his celebrity - getting a big contract, winning one famous game, being the first pro football player to wear pantythose in public - not for achievements on the football field." - comment at Football Outsiders.

Is this true? Let's see. Before examining his 1972 numbers in some detail and putting them in 2010 terms, a few other facts...

* In 1967 Namath became the first QB to break the 4,000-yard barrier. His 4,007 yards weren't matched until after the season was lengthened to 16 games and the passing rules were liberalized, a dozen years later. Those 4,007 were 42% more than the pro average, as 5,351 would have been in 2010 (the all-time record is 5,084) - so it's easy to see the electric impact they had on the football world.

* selected Namath's famous shoot-out victory over Unitas and the Colts in 1972 as the Best Single-Game QB Performance Since 1970. (some video of the game)

* What matters is a QB's (and team's) performance relative to competitors. This can be measured by standard deviation, which can be used to produce corresponding numbers relative to average across eras.

For instance, Namath's 3,147 yards passing in 1968 (the year of Super Bowl III) was 1.28 standard deviations above the pro average. During 2006-10, 1.28 standard deviations above average was 4,198 yards. Making the corresponding adjustment for attempts, completion%, yards-per-completion, Int%, TD%, and sack% we can generate annual number lines for Namath's career in 2000s terms that relative-to-average are the same as his numbers were in his own day.

If we then take Namath's five best years total and compare it to corresponding totals of QBs in the post-1978 rule change era, we can gain some perspective on how his performance compared to theirs.

I did this with ten of the top post-1978 QBs. Namath had only seven mostly healthy full seasons in a 13-year career, so he's handicapped in this comparison compared to QBs who played many more healthy seasons (for Favre we'd pick the best 5 of 20). To equalize the playing field a bit, I took his five highest-yardage seasons and the five highest-yardage of the first 13 seasons in the careers of the other QBs. (The 5-of-first-13 selection had no effect on any active QB, and only minor effect on the others apart from Favre.) Result:

All 11 QBs are ranked in three categories: total yards; yards/attempt as a measure of efficiency; and ANY/A to adjust for TDs, INTs and Sacks. "Score" is combined rankings in all categories, so smaller is better.

Top 5 years YDsY/AANY/AScore
Manning 22567 (3) 7.92 (3) 7.78 (1) 5
Young 18827 (10) 8.24 (1) 7.50 (2) 13
Rivers 19513 (8) 8.04 (2) 7.30 (4) 14
Brees 22918 (1) 7.66 (9) 7.10 (5) 15
Marino 22854 (2) 7.68 (8) 7.02 (6) 16
Namath 21123 (4) 7.80 (5) 6.76 (7) 16
Fouts 20997 (5) 7.90 (4) 6.50 (9) 18
Brady 20978 (6) 7.61 (10) 7.38 (3) 19
Montana 18702 (11) 7.80 (5) 6.76 (7) 23
Favre 20536 (7) 7.74 (7) 6.42 (10) 24
Elway 18907 (9) 7.02 (11) 6.08 (11) 31

There's nothing scientifically precise about this and it doesn't pretend to be any kind of definitive ranking. But there's absolutely no indication here that Namath wasn't fully in the class of these later HoFers and likely HoFers-to-be, relative to his competitors of his own time.

Now for the 1972 season.

We can be more precise looking at a single season. Namath's 1972 is convenient because it wasn't his best, so it can be considered representative, and it was his first healthy season after the AFL-NFL merger, so no "AFL adjustments" are needed.

Namath's actual 1972 numbers:

Attempts 324
Completions 162
Comp % 50.00%
Yards 2816
TDs 19
INTs 21
Sacks 11

Posnanski sees a meager 50% completion rate, only 2,800 yards, that negative TD-pick ratio, plus a passer rating of only 72.5, and says "Yuck!" replied in defense of Namath's honor, saying about 1972:

"He led the league in passing yards, touchdowns, yards per attempt, adjusted yards per attempt, net yards per attempt, and adjusted net yards per attempt. Oh, and he completed only 50% of his passes, so he sucked."

Namath's TD-pick ratio wasn't bad enough to prevent him from being #1 by ANY/A, which subtracts 45 yards for every interception, and he was #2 in sack rate.

And unmentioned (as always) is the "killer stat" of the era, yards-per-completion. Namath was #1 in that too, with his 17.4 yards each being was four standard deviations(!) above average. That number that has never been matched since, and likely never will be unless they change the rules again. (The highest Y/C of the 2000s has been 14.7 by Donovan McNabb in 2006.)

On to the regressions. By the passing game coefficients for 1971-5, Namath's passing numbers are at a .767 winning percentage level of play. For perspective, the passing game coefficients for 2006-10 give the performances of the top five QBs of 2010 by passer rating as being at these winning percentage levels...

Brady 0.714
Rivers 0.680
Rodgers 0.663
Vick 0.620
Roethlisberger 0.653

Now to convert Namath's 1972 to 2006-10 levels in two ways. First is the simple adjustment by standard deviation, mentioned earlier. Taking Namath's standard deviations over/under average for all the rate figures and for attempts per game, and multiplying by 16 games of attempts, we get...

Namath's 1972 adjusted to 2010 by SD:

Attempts 515
Completions 304
Completion % 59.0%
Yards 4378
TDs 28
INTs 19
Sacks 12

In 2010 these numbers would have ranked: by attempts #9; TDs #6, yards #4, yards-per-attempt #2, yards-per-completion #1 (obviously, four standard deviations above average), sack percentage #2, ANY/A #2.

"Shockingly bad"? You decide.

But there are problems with these numbers. Although they are accurately adjusted relative to average, the ratios among them were set in an earlier era when yards-per-completion was the winning stat, and teams won by accepting the lower completion rates and higher interception rates that came with longer throwing. That's shown by the huge yards-per-completion anumber combined with below-average completion percentage (23rd) and TD-Int ratio (18th) -- and also by the 2006-10 passing coefficients, which drop these numbers from a .767 level of play to a .724 level.

Don Shula called Namath "one of the three smartest quarterbacks of all time". A QB that smart wouldn't keep hurling the ball deep after the key to winning changed to high-percentage passing with a high TD-Int ratio. (Nor would his coaches let him!) What would Namath's numbers look like with modern game planning?

To reach a guestimate I expanded the numbers above by increasing all the standard deviations proportionately (thus further increasing yards per catch, while reducing completion percentage, etc.) until the net result was a .767 level of play by the 2006-10 passing coefficients - then reduced yards-per-catch while improving completion percentage and interception rate proportionately in the amount needed to maintain the .767 level of play. Rather arbitrarily, I set yard-per-completion high enough to remain #1 by half a yard, at 13.8 - still quite high (hey, the guy liked to throw long!) but not absurdly so. The result...

"Modern Namath"

Attempts 515
Completions 321
Completion % 62.3%
Yards 4430
TDs 28
INTs 15
Sacks 8

The change is modest overall, but now both completion percentage and the TD-Int ratio are above average, while the other rankings are: yards #4, yards-per-attempt #2, yard-per-completion #1, sack percentage #1, and ANY/A tied for #1.

Whether Joe would actually have played this way if miraculously transported through time to 2010 from 1972 nobody can ever say.

But the regressions do say that Namath's .767 level of play in 1972 was equivalent to this as the .767 level of play in 2006-10.

One more closing thought about Namath: NFL football is a team game, the performance of the team has a significant effect on the QB's numbers. Brady, Rodgers, Brees, Rivers, and Roethlisberger, the top-rated QBs in 2010, all piled up their numbers with the support of winning-quality teammates - Brady's team played a season without him and won 11 behind a sub who hadn't started a game since high school. Namath in 1972 played on a bad team that finished only 7-7 and would have gone 3-11 or 4-10 without him.

The moral of the story

The purpose of all this is not to prove that Joe Namath was a great QB - it's really not about Namath at all.

The main point is that when we use measures that matter to us today to evaluate the past, without realizing that the measures that mattered then were different, we are prone to making serious mistakes. And among football fans this has caused many of the greats of yesteryear to be seriously under-appreciated today, as the earlier parts of this story have pointed out. Recapping...

* Yards-per-attempt, a credible measure of passing performance today, becomes steadily less so when applied backward in time as yards-per-completion becomes more important, because it obscures whether yards are coming from high yards-per-completion (relatively good) or high completion percentage (relatively bad).

* Passer rating is outright perverse when applied back to the years when yards-per-completion trumped completion percentage in winning value. Its bias in favor of completion percentage over yards gained is ... unfathomable.

An example speaks more than words. Three QB performances and their ratings...

10 of 10 -100 yardsY/A -10.0rating 79.2
6 of 10 +45 yards Y/A +4.5rating 70.8
4 of 10 +80 yards Y/A +8.0rating 68.8

'Nuff said about passer rating.

A second point is that the opinions of those who witnessed and experienced events in the past should not be glibly dismissed just because we know we're smarter.

A generation of MVP, All-Pro and Pro Bowl voters deemed John Unitas the dominating QB of his era. Today a well known football stat site looks back with revisionism and declares Starr absolutely the much better QB because of his better passer ratings and occasionally higher yards-per-attempt (though they tied, career-wise). If that site had paused to ask, "Why did the people who actually saw these two play, and who played against them, have such a different opinion?", it might have figured out that there is a problem with passer rating and have had something worth writing about. Instead, it just repeats itself peddling soft-headed football tripe to whoever will buy it.

We may indeed know more than did the people of days gone by, overall. I hope so. But what they knew and we've forgotten counts too.


Chris said...

Great series! I thought it was awesome to look back at what stats won in the past. Very nice!

Anonymous said...

Brilliant set of posts. Really quite important. Well done.

Anonymous said...

Excellent work!

Anonymous said...


As someone who never watched Namath play, and as someone who intensely dislikes the Jets, I was absolutely one of many that jumped on the "Namath was/is terrible" bandwagon. His numbers looked awful! Absolutely, I was confident that his HoF appearance had to do with that game, and less with his overall performance (I was willing to admit that his performance in that game was stellar). In fact, I was willing to concede that he deserved to be in the Hall of Fame only because winning that game was probably quite important to moving the merger forward, but not because he was a good QB (We can't only induct "Good Rex" into the Hall of Fame, for example).

I think this series of posts radically changes my understanding of the argument. Very eye-opening indeed. I'm willing to concede that he was a very good QB. And I'm certainly willing to re-evaluate my understanding of stats from previous eras. A commenter on a previous post indicated that different eras had different "killer stats" and perhaps it'd be interesting to expose those. It's always fascinating to confront assumptions one didn't even know one had.

I still hate Joe Namath, though.

Thank you

Statalyzer said...

Namath is still really overrated. All because he said "I guarantee we'll win" and then sat back and mostly watched his defense win the game and not get their fair share of credit for it (much like Brady in the Super Bowl win over St. Louis but without the guarantee).

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