Tuesday, February 20, 2007

A Yard is a Yard

A few weeks ago, Doug Drinen posted a study on his blog starting here- http://www.pro-football-reference.com/blog/wordpress/?p=243 that looked at evidence of irrational coaching behavior, by looking at the difference between run/pass distribution on 2nd and 10, depending on whether the previous unsuccessful play was a run or a pass.

That post got me thinking about other potential examples of irrational coaching behavior, and the first circumstance that came to mind were 4th and 1 situations after a team was "stuffed" on the previous 3rd down play and failed to get the first down. My impression is that coaches get a little more conservative in this situation than, say, if they get stuffed on first down and then get to 4th and 1 after a pass. I think there is probably some mentality of not wanting to fail back to back that keeps coaches from going for it in this situation as often as they should.

Before I get to the numbers, some other thoughts. A run that would be classified as a 1-yard run if it occurred on 2nd and 6 would be classified as a 0-yard gain if it occurred on 3rd and 1, even if it gained a full yard or close to it, if it failed to make it past the first down marker. Thus, I would expect that 4th and 1's resulting from 0-yard rushing gains on 3rd down would be, on average, closer to the first down marker than other 4th and 1's. How much closer I cannot say, but it seems intuitive to me that some percentage of these 0-yard gains actually moved the line of scrimmage closer to a first down.

On the other hand, I would expect 4th and 1's resulting from officially recorded positive gains to be more randomly distributed, ranging from 4th and inches to almost 4th and 1 and 1/2 yards. Thus, if all else was equal, and there was no bias against going for it after being stopped with little to no gain on the previous play (and if the relative distance of a 4th and 1 was a determining factor), I would expect that the attempt rate and success rate on 4th and 1 following failure on 3rd and short to be, at least to some degree, greater than following 3rd and medium or long plays.

Now to the actual numbers from the 2006 seasons, with a couple of caveats. I looked at all 4th and 1 opportunities between the opponent's 40 yard line and the opponent's goal line, with the thought that this was the area where teams are actually willing to go for it. I excluded plays occurring in the last minute of each half. I counted it as an opportunity even if a team took a delay of game penalty, with the thought that this was a conscious decision "not to go for it" by the team in question. I did not count it if there was another pre-snap penalty (false start, e.g.). If a team attempted to go for it, but was called for an accepted offensive penalty during the play, I counted it as an attempt, but did not count it against the success rate. The thinking here is that it is neither a success nor a failure in the same sense that conversion vs. failed attempt is, because the team could then punt or attempt a field goal. However, it was an "attempt" because the intent of the coach was clearly to go for it.

Here are the numbers, broken down by field position. The first number is the total number of opportunities, the second number is the attempt percentage (attempts/opportunities) and the third number is the success percentage (conversions/total attempts (minus above caveat)).

4th and goal from the 1

  • 1 yard or less gained on 3rd down 23/ 0.696 /0.500
  • 2 to 4 yards gained on 3rd down 8 /0.625 /0.800
  • 5 or more yards gained on 3rd down 6 /0.500 /1.000

4th and 1, 10 yard line or in (excluding goal to go)

  • 1 yard or less gained on 3rd down 17 /0.412 /0.833
  • 2 to 4 yards gained on 3rd down 6 /0.500 /0.667
  • 5 or more yards gained on 3rd down 16 /0.438 /0.571

4th and 1, 11-20 yard line

  • 1 yard or less gained on 3rd down 16 /0.125 /0.500
  • 2 to 4 yards gained on 3rd down 9 /0.333 /0.667
  • 5 or more yards gained on 3rd down 10 /0.500 /0.600

4th and 1, 21-30 yard line

  • 1 yard or less gained on 3rd down 18 /0.500 /0.875
  • 2 to 4 yards gained on 3rd down 8 /0.625 /0.800
  • 5 or more yards gained on 3rd down 18 /0.611 /0.636

4th and 1, 31-40 yard line

  • 1 yard or less gained on 3rd down 24 /0.708 /0.824
  • 2 to 4 yards gained on 3rd down 11 /0.818 /0.556
  • 5 or more yards gained on 3rd down 18 /0.944 /0.688

4th and 1, all between opponent's 2 and 40 yard line

  • 1 yard or less gained on 3rd down 75 /0.467 /0.818
  • 2 to 4 yards gained on 3rd down 34 /0.588 /0.650
  • 5 or more yards gained on 3rd down 62 /0.645 /0.641

Now, I cherry-picked out the goal line situations, where the majority result from short to no gains on the previous down. Here, I think the rationale is different. In my subjective opinion, if there is something NFL coaches as a group love, it is to pin the opponent on the goal line. An overinflated sense of being able to pin the opponent deep must be what drives some coaches to punt on 4th and 1 from the opponent 36, for example. And so here, success is immediate gratification, and failure leaves the other team snapping in their own end zone.

As for the remainder of 4th and 1 situations, the coaches for teams that gained little yardage on 3rd down are going for it less frequently, but being far more successful when they do, suggesting that the 4th and 1 attempts may be closer on average. More data is necessary, but it appears that in 2006, coaches who were stuffed on 3rd down were more conservative on fourth down than their peers.

FYI, here are the teams with the most times facing 4th and 1 following a no gain play on 3rd and 1:

Green Bay - 5

Dallas - 4

Detroit - 4

Oakland - 4

Washington - 4

Monday, February 12, 2007

Does Saunders create bad defense?

This was posted on the KC Chiefs website by Bob Gretz on January 19, 2007, in an article about defensive rankings:

"WASHINGTON’S DEMISE: Could it be that what the Chiefs proved for the better
part of five years and what the Redskins showed in 2006 is that it’s
impossible
to have a good defense when Al Saunders is your team’s offensive
coordinator?


There are plenty of people in the NFL, and around Arrowhead
Stadium,
who don’t think it’s a coincidence that when Saunders took over
preparing
the offensive game plans for the Redskins, their defense turned in a
very
bad season. . . . "

I hope he is joking. Al Saunders, offensive coordinator of one of the best offenses in the league, was apparently responsible for the Chiefs horrible defense. It had nothing to do with the GM spending early picks on Ryan Sims, or Eddie Freeman, or William Bartee. It had nothing to do with playing Eric Warfield and Dexter McCleon. Or having no edge pass rushers like the current tandem of Jared Allen and Tamba Hali during 2001-2003. Oh, and Saunders apparently made Adam Archuleta suddenly become terrible, depleted the Redskins depth due to continuous trading of draft picks in seasons he was not there, and injured their starters through his poor game planning.

Amazing. I would try to rebut this with actual statistics, but what is the point. Clearly, Gretz is the master of correlation versus causation.

Saturday, February 10, 2007

Home Field Advantage and Passing

This is a follow up to the previous post, in which I looked at home and road won-loss records of all teams finishing between 6-10 and 10-6 for the years 1995-2006.

Here are the pass offense stats:

  • below 6.0 - 18 teams; .576 at home; .299 on road
  • 6.1-6.3 ypa - 34 teams; .563 at home; .419 on road
  • 6.4-6.6 ypa - 43 teams; .583 at home; .407 on road
  • 6.7 -6.9 ypa- 35 teams; .577 at home; .423 on road
  • 7.0-7.2 ypa - 29 teams; .591 at home; .425 on road
  • 7.3-7.5 ypa - 25 teams; .605 at home; .455 on road
  • 7.6-7.8 ypa - 14 teams; .580 at home; .455 on road
  • 7.9 and up - 12 teams; .667 at home; .469 on road

And here are the pass defense stats

  • below 6.0 ypa - 22 teams; .591 at home; .438 on road
  • 6.1-6.3 ypa - 35 teams; .636 at home; .443 on road
  • 6.4-6.6 ypa - 46 teams; .598 at home; .428 on road
  • 6.7 -6.9 ypa- 48 teams; .560 at home; .422 on road
  • 7.0-7.2 ypa - 34 teams; .581 at home; .414 on road
  • 7.3-7.5 ypa - 14 teams; .589 at home; .321 on road
  • 7.6-7.8 ypa - 4 teams; .563 at home; .406 on road
  • 7.9 and up - 7 teams; .464 at home; .339 on road

Teams improve their overall record as pass defense improves, but the difference between home and road performance stays fairly constant. The same is generally true of the pass offense as well. However, the 18 teams that were "poor" offensive passing teams (ypa 6.0 or lower) were horrible on the road while being decent at home.

As a result, I looked at teams who were below average in passing, while also being good at stopping the run. Here are the teams from the bottom passing offense groups of 6.6 ypa and below, sorted by their rushing defense numbers:

  • 3.5 or below - 13 teams; .615 at home; .365 on road
  • 3.6 - 3.8 ypc -30 teams; .594 at home; .350 on road
  • 3.9 - 4.1 ypc -24 teams; .583 at home; .443 on road
  • 4.2 - 4.4 ypc -18 teams; .528 at home; .396 on road
  • 4.5 and up - 9 teams; .542 at home; .417 on road

To summarize, the top 2 groups on this list are the below average passing offense, but above average run defense teams. Those 43 teams had a +.246 difference in their home winning percentage versus the road winning percentage, which equates to almost 2 more wins at home on average over the course of a season.

It appears that these types of teams (bad offense, good rush defense) have a greater road disadvantage because of the offense, but a greater home advantage because of the rush defense, creating a greater home/road differential.

Home Field Advantage and Rushing

Using the pro-football-reference.com database, I looked at all teams that finished between 6-10 and 10-6 for the years 1995-2006. Why those records? It's partially arbitrary-- I could have just as easily narrowed it to 9-7/7-9, or expanded it to 11-5/5-11. But my goal was to look at the middle class of the NFL, teams that generally have some strengths but also some flaws. I felt this dividing line would accomplish that.

I then compared some of the standard rate stats, such as rush yards per attempt and pass yards per attempt, to see what team characteristics, if any, contributed to a greater difference between home and road winning percentages. This post will focus on the rushing stats, both offensive and defensive.

210 total teams finished between 6-10 and 10-6 during the 12 seasons reviewed, an average of over 17 per season--so slightly more than half the teams in the league on average. The entire group averaged winning .586 at home and .417 on the road, for a +.169 difference between home and road winning percentages. This would equate to +1.36 more home wins than road wins over the course of a 16 game schedule.

Here are the numbers divided by offensive rush yards per carry:
  • 3.5 and below - 32 teams; .582 at home; .398 away
    3.6 to 3.8 ypc - 34 teams; .590 at home; .408 away
    3.9 to 4.1 ypc - 63 teams; .567 at home; .423 away
    4.2 to 4.4 ypc - 40 teams; .591 at home; .417 away
    4.5 and above - 41 teams; .611 at home; .431 away

Here are the numbers divided by defensive rush yards allowed per carry:

  • 3.5 and below - 26 teams; .611 at home; .399 away
  • 3.6 to 3.8 ypc - 47 teams; .625 at home; .380 away
  • 3.9 to 4.1 ypc - 57 teams; .605 at home; .425 away
  • 4.2 to 4.4 ypc - 41 teams; .537 at home; .419 away
  • 4.5 and above - 39 teams; .548 at home; .460 away

There is basically no indication that simply running the ball better on offense, without any other info, either increases home field advantage or reduces road disadvantage.

Unlike the offensive numbers, the defensive numbers appear to show a difference between how the "middle class" performs at home vs. on the road, depending on whether the team is good at run defense or not. Teams that are not particularly good at stopping the run show less difference in how they perform at home vs. on the road.

If the strength of rush defense does increase home field advantage, there is a potential explanation. If a team is better at stopping the run, it is conceivable that such a team would be somewhat more likely to place its opponent into more 3rd and long situations. This might translate to a bigger advantage at home, where the offense is subject to crowd noise, than on the road, where the home crowd would presumably be quiet to aid the offense. Of course, we also need to keep in mind that this is looking at some of the variables. A team that is poor at stopping the run, yet finishes in the middle, likely has strengths in other areas to compensate. A team that is good at stopping the run, but does not finish in the upper tier, also likely has some other flaws that may be combining to create road disadvantage as well.

Next time, I will play with the passing numbers, overall offensive numbers and overall defensive numbers.