Which Teams Should Abandon the Run?

Yeah, yeah, yeah. It's a passing league. We got it. And still, according to the numbers, teams aren't passing enough. In the cases of some teams, it's painfully obvious that they should be passing more and running less. As a Ravens fan, I watched another game where nearly every run was simply a wasted down. Most of their paltry positive rushing yards seem to come from trash draw plays on long distances to gain, intended to mitigate very poor field position prior to a punt. It's like they're playing with two or three downs when everyone else gets four.

I wonder if, at some point, when an offense is so much better at passing than running, should it abandon the run almost altogether. On top of the general imbalance in the league, some teams are just throwing away downs when calling conventional run plays. Of course, running and passing generally play off of each other in a game-theory sense. To be successful, passing needs the threat of running, and vice versa. But sometimes, the cost of running is so high for some offenses, that it would be worth the trade-off to forfeit the unpredictability and just pass nearly every down.

It sounds crazy, but take a look at the Expected Points Added per play so far this season (through the 1pm games on Sunday 10/13). The right-most column is the pass-run split. The bigger that number, the greater the imbalance. Pay particular attention to the teams highlighted in red:

Demise of Running?

Longtime reader Eddy Elfenbein wrote me last night about the continuing demise of running in the NFL. From his own site:

The season is still young so this trend may not last, but with two weeks on the books, the number of rushes-per-game is down 4.8% from last year.

But what’s really dramatic is that average yards-per-carry is down by 10.7% (from 4.262 to 3.805).

Combine the two effects, fewer runs going not as far, and the rushing-yards-per-game figure is down 15% from last year. That number has been fairly steady for the last 25 years.

On the passing side, attempts are up 7.8%, completions are up 10.0% and passing yards are up 10.5%. The league-wide passer rating now stands 87.3. In 1994, that would have qualified as fourth-best in the league.

I'm surprised league-wise rushing yards per carry is so low. I don't recall anything below 4.1 YPC, even this early in the season. Aside from that, everything else is part of a continuing trend--something game theory predicts will continue.

Running to Create a 'Manageable' 3rd Down Is Self-Defeating

Note: this is a companion article to last week's column at the Washington Post.

One of the common defenses of a run-heavy offense is that offenses need to make their third downs “manageable,” meaning short enough so that conversion is easier. The thinking goes that if an offense runs on either or both first and second down, it is relatively assured of shorter rather than longer distances on third down. At first look, this makes a lot of sense. After all, who wants to face third and long?

There are two problems with this argument. The first is that football is not a game of piling up first downs. The days of inching toward the goal line on 18-play drives are long gone if they ever existed at all. Football is, for the most part, a game of maximizing score differential, and the concept of Expected Points shows that NFL offenses are generally running too often on first and second down.

The second problem is that even if gaining a first down is the primary objective, running on first down is becoming a worse idea every year. The graph below shows that passing on first down leads to a conversion more often than running on first down. As usual, I limited the data to plays in ‘normal’ football situations, when the score is relatively close and time is not yet a factor at the end of either half.

Washington Post: 'Manageable Third Downs'

This week's article at the Post looks at how third down conversion rates can mislead coaches into poor strategic approaches.

Offenses are better off thinking of their three downs (and fourth when the situation requires) as isolated opportunities for ten-yard conversions rather than stepping stones toward what coaches call a “manageable third down.” The best third down situation isn’t third and 1 or even third and inches. It’s converting on first or second down, before ever reaching third down. Rather than seeking a short third down situation, offenses should be avoiding third downs whenever possible.

Expect Even More Passing Yards, and Why It Matters

Remember the passing explosion to start the NFL season last year? Get ready for even more. 2011 was not a one-year blip but instead was part of an accelerating trend toward more potent and more frequent passing. This isn't statistical trivia either, as this trend has dramatic implications for how the game should be played.

Take a look at Adjusted Net Yards Per Attempt (courtesy of PFR), which with just one number incorporates passing efficiency, interceptions, and sacks. Since the dawn of the modern passing era, passing has become steadily more lucrative. But since 2004, the rate of increase in average ANY/A has accelerated. The 2011 season featured the most successful passing game ever.

For context, compare the graph above with the next one. This shows the same trend but for rushing yards per carry. There is a very shallow increasing trend since a trough in the mid 1990s, but it pales in comparison. The jump in net passing last year alone is larger than the increase in rushing over the entire period. (I've kept the scales of both graphs identical for a pure comparison.)

Weather Effects on Passing

My last post looked at the effect of temperature on home field advantage. We saw that cold weather put dome and warm climate teams at a disadvantage. The post was titled How Does Temperature Affect Road Teams?, but I really didn't answer that question. I measured the size of the effect, but I didn't solve the riddle of actually how temperature makes a difference. This post will begin to look at just how weather makes a difference, starting with the passing game.

Here's how passing fares for home and visiting teams by temperature. The chart below shows  Adjusted net Yards Per Attempt (AYPA), which accounts for sacks and interceptions, according to temperature. Keep in mind there are smaller sample sizes at the extremes.

Brees versus Marino, 2011 versus 1984

On Monday night we saw history. Drew Brees eclipsed Dan Marino's record of 5,084 total passing yards on a late-game touchdown pass to Darren Sproles. Regular readers know that I'm no fan of most ever or least ever records because they're usually just trivia that end up giving the word 'stats' a bad name. Readers also know that total passing yards is not a particularly meaningful way of measuring a quarterback's skill. But it's hard to let the occasion pass without taking note.

The Monday Night Football crew did a good job of reminding viewers of the context of the record, even going as far as providing analysis showing how far above average both Marino's and Brees' were for their respective seasons. The NFL's passing numbers have steadily inflated over the years, largely due to rule changes that favor offenses. But like many other sports, it's possible that the athletes have simply improved over time. Defenders can improve too, but who's to say that athletic improvement on both sides of the ball doesn't disproportionately favor the offense. The fact is we simply have no way to tell.

We can use some statistical tools to get a feel for how outstanding each season was. Drawing the line at the top 30 passers in both seasons, we can calculate the number of standard deviations Marino and Brees stand above the season average. Marino's 1984 was 2.4 standard deviations above average, while Brees' 2011 (so far) is 1.9 standard deviations above average. Marino achieved his numbers on 564 attempts while Brees has 622 attempts, and counting. Brees has 13 interceptions compared to Marino's 17. According to PFR's Adjusted Net Yards Per Attempt, which factors in yards, attempts, interceptions, and touchdown passes, Marino beats Brees 8.9 to 8.0.

One of the unspoken assumptions when discussing Marino's 1984 record is that his record is a 'pure' or 'true' record, and the record set in 2011 is asterisked by the liberal passing rules of today's NFL. But do you know who's record he broke and when that was set? It was Dan Fouts in 1981. Before that the record belonged to...Fouts in 1980. And before that...Fouts in 1979. But prior that, the pro record was an AFL mark set by Joe Namath in 1967.

Identity Crisis

If there’s one meaningless word thrown around by football analysts in the last couple years, it has to be identity. “The Jets offense has an indentity crisis.” “The Ravens need to find their identity on offense.” “The Eagles have lost their offensive identity.”

Are we talking about professional football teams or teenagers trying to figure out whether to hang out with the jocks, dweebs, preppies, or wastoids?

Identity has replaced rhythm as the most meaningless word in the NFL. Remember those days when every broadcaster at one point in the game had to say, “The 49ers need a couple of completions here to get into a rhythm"?

What the hell does that even mean?

Deadspin/Slate Roundtable: Passing in 2011

Here's a second post in the roundtable series at Slate and Deadspin. This one encapsulates and updates my recent look at the causes of the passing explosion in 2011. It's a little more readable and entertaining than the original graph-filled post.

What Happened to the First Round RB?

In the five-year period between 1970 through 1974, running backs made up 20% of all first round NFL draft picks. That's one out of every five. As recently as the 1985-1989 period, RBs made up 19% of first rounders. But by the most recent decade, from 2000 through 2010, RB selection was cut in half--down to about 10%. Last night, only 1 of the 32 players chosen (about 3%) was a RB, and he was chosen 28th, near the bottom of the round.

The graph below illustrates the trends in how teams favor each position over the past 41 years. Most positions are fairly stable. Click to expand.

Tables vs. Graphs

I'm not sure about everyone else, but I've got a very visual brain. I'm one of those guys at work who can't have a conversation without going to the whiteboard, if only to organize my own thoughts. I don't think I'm alone, either. Many theorists believe one reason humans became such smart monkeys is that we co-opted the huge visual-spatial part of our brains to use for abstract thought.

The concept of time is one example. We think and talk of time, a concept virtually without its own terminology, in terms of space and motion: Time goes by...Our best days are ahead of us...I'm looking forward to next season. The blathering talking heads on CNBC can't go 20 seconds without convulsively saying the phrase going forward whenever referring to the future.

Abstract sports concepts like win probability are no exception. We would all call 2-yard run on 4th and 1 a big play, even though it was anything but literally big. How would we characterize a 38-35 game? As a high-scoring game, of course. We are universally comfortable speaking about abstract concepts in terms of the metaphors of physical position, size and motion, and it's a window into how we think. That's why I'll take a graph over a table of numbers any day.

Plotting Run vs. Pass Success Rates (And How to Beat NE)

It might be a little late in the season for stuff like this, but better late than never. Often we can learn a lot by taking information we already have and graphing it. In this case, I've taken each team's Success Rate (SR) stats for running and passing and plotted them against each other.

As you might recall from a post early in the season, SR is one stat where passing and running actually correlate, suggesting that "success" is the component of performance that coaches try to optimize. Simply put, from the perspective of game theory, it's how we can tell that running "sets up the pass" and vice versa. SR for both running and passing is also a reliable predictor of team success, i.e. winning.

If we plot each team's pass SR by its run SR for 2010, we should expect to see a correlation, represented by a diagonal trend. The better teams will be on the top and right, while the worse teams will be on the bottom left. Also, we would not expect to see many teams that are very good in one aspect, either running or passing, but not any good in the other.

Almost Always Go for 2-Point Conversions?

In the Buccaneers-Redskins game this past Sunday, the Redskins were able to score a potentially game-tying touchdown at the end of regulation, only to fail to hit the extra point due to a mishandled snap. Gregg Easterbrook suggested the Redskins should have gone for the two-point conversion, which is a plausible strategy in many circumstances. But Easterbrook went on to add this little tidbit: "Rushing deuce attempts are about 65 percent successful in the NFL -- a better proposition than the 50/50 of advancing to overtime."

It's well established that 2-point conversion attempts are successful slightly less than 50% of the time, so could the 65% number for runs possibly be true? If so, what would that mean for NFL strategy?

There have been 718 2-point conversion attempts from 2000-2009, including playoff games. Overall, they've been successful 46.3% of the time. But this is slightly misleading because it includes aborted kick attempts. If we weed those out, along with some other mysterious plays, such as Josh McCown's kneel-down while trailing by 5 points in the final few seconds of the Cardinals-Vikings 2003 game, we get a different answer. For all normal 2-point conversions, the success rate is 47.9%.

Now look at the success rate broken out by play type:

Deep vs. Short Passes

Over the past couple years, we've learned that passing well is  more important than running well in terms of winning games. We've learned that passing has become more and more lucrative over the years. And we've learned that offenses should pass more often, particularly outside the red zone and on 1st down. But 'passing' is a large category, encompassing everything from a screen pass 2 yards behind the line of scrimmage to a 50 yard bomb. 

Beginning in 2006, the NFL classified every pass attempt as either 'short' or 'deep,' where deep means anything past 15 yards. About 19% of pass attempts are classified as deep. Unfortunately, that's all we get, so we can't tell a screen from a 14-yard down-field pass attempt. Still, it allows us to begin to pull apart different types of passes and examine them in one more layer of detail.

In normal football situations, in which the clock is not yet a factor and the score is relatively close, pass plays, including sacks, yield an average of +0.08 Expected Points Added (EPA), while run plays yield an average of +0.01 EPA. Which type of pass is more responsible for that advantage, risky deep passes or safer short passes?

What Is the Break-Even Run Success Rate?

I've been looking at run Success Rate (SR) lately, and it appears to be a fairly important indicator of team success. But if I said that a particular team's run SR was 45%, how would you know if that's any good? It's less than 50%, so does that mean it's bad? So I decided to plot Expected Points Added (EPA) against SR to find out where the break-even point is.

When I plot run EPA per play vs. run SR (for 2000 through 2009), the break-even point is where the best-fit line crosses EPA/P axis--just above 41%.

How Coaches Think: Run Success Rate

Before tools such as EPA and WPA were available, I relied on team efficiency stats to estimate team strength. Yards per pass attempt or per run attempt worked out to be very good estimators of how good a team was, especially if ‘good’ is defined as being likely to win forthcoming games. Efficiency stats had the added benefit of being relatively simple, widely available, and easy to calculate.

Efficiency stats also worked well in regression analysis. In a regression model, it’s best if the predictor variables are independent of each other. In other words, the less each predictor variable correlates with the others, the more valid and reliable the resulting model will be. Passing and running efficiencies in the NFL correlate weakly. Over the past 10 seasons, offensive passing and running efficiencies for each team correlate at 0.09 (where 1 would mean lock-step correlation and 0 would mean complete independence.)

Passing = Winning

Advanced NFL Stats owes its start to an old water cooler debate: What's more important, offense or defense? Running or passing? A few years ago, I still had some statistical software left over from grad school loaded on my laptop, so I thought, "Hey, maybe these are questions that can be definitively answered." I tried to answer those questions with one of my original posts three years ago, What Makes Teams Win. When I read my older stuff, I sometimes want to cringe, but not with that one. It holds up very well, and it's well worth revisiting for newer readers, this time with more data. In this post, I'll do just that, focusing on the relative importance of running and passing.

When I was little, my dad taught me the inanity of the 'running leads to winning' fallacy. We'd watch a game on Sunday, and invariably we'd hear the announcers talk about how a team always wins when their star RB got at least 25 carries or so. They'd wax poetic about the noble nature of pure, old-fashioned, run-it-up-the-gut football. My dad would say, "Yeah, by that logic, teams should start kneeling in the first quarter. Kneeling leads to winning, right?"

Run-Pass Balance--A Historical Analysis

I’ve been writing a lot about run-pass balance lately, and part of my theory of why teams are perhaps passing less often than they should has to do with the evolution of the sport. Rule changes over the recent decades have generally favored passing. Changes in pass blocking rules and in pass interference rules have made it easier to pass the ball successfully. Even subtle rule changes such as the definition of possession and “control” may have made receiver fumbles less likely.

Tactics and play selection have been refined over the years to take advantage of the rule changes, but I’m not sure that they’ve completely caught up. Results from several studies, including my own, have suggested that in most situations, passing is more lucrative than running. This imbalance implies that passing should be selected more often. As defenses respond to expect more frequent passing, the payoff for passes will decrease as the payoff for runs increases. Eventually, there is an equilibrium where the payoffs should be equal.

In this post, I’m going to look at very simple historical trends. As you’ll see in the graphs below, there is evidence that the current run-pass balance has not responded fully to recent increases in the payoff of passes. All data come from PFR's very cool league historical pages.

Run-Pass Imbalance In the Red Zone--1st Downs

Just before halftime in last year's Super Bowl, on first and goal from the one, Kurt Warner threw the ball directly into the arms of James Harrison who rumbled 100 yards for a touchdown. With so little time left in the half, passing was the obvious call, but that play highlights the dangers of passing so close to the goal line.

Game theory tells us that when payoffs for strategies are unequal, the strategy with the higher payoff should be chosen more often. We've seen that between the 20 yard lines payoffs for passes are consistently higher than for runs on 1st down, but inside the 20 running becomes more lucrative. Now let's take a look at the red zone in more detail, where the stakes get higher and the field gets shorter. On 1st downs in the red zone, should offenses run or pass more often, or do they already strike the right balance?

Run-Pass Imbalance on 2nd and 3rd Downs

I've recently been looking at the imbalance in the payoffs for running and passing on first downs. The results suggested that most teams should generally pass more often outside the red zone and run more often inside the 10-yard line. What about 2nd and 3rd downs?

Game theory tells us that when the payoffs for two strategy options are unequal, the strategy option with the higher payoff should be selected more often. As the opponent adjusts to counter the new mix of strategies, the payoff of the favored option will decline while the unfavored option becomes more lucrative. Eventually, the payoffs for both options equalize, and at this point the overall payoffs are optimum. In two-player zero-sum games this is known as the minimax, or more generally as the Nash Equilibrium.

I used Expected Points (EP) to value the payoff of each play. Expected Points measures the net point advantage that the play result gives to an offense. It captures the value of yardage gained and lost, first downs, sacks, penalties, turnovers, and everything else in terms of equivalent point value. The change in EP resulting from a play is called Expected Points Added (EPA).

One of the things EP does not measure is the time value of a play. In situations when a team has a significant lead, the true value of a run includes the time burned off the clock. To a team behind late in a game, pass attempts have more value because they are more likely to stop the clock. For this reason I only include plays in the first and third quarters and when the score is within 10 points. This excludes trash-time plays and plays affected by the clock.