Tuesday, May 8, 2012

Weighted Yards: The new way to measure an NFL offense.


            How should we measure the success of an NFL offense? Yards and points are the two most common measures but they don’t tell the whole story, not even close. If two teams are playing in the wild card round of the playoffs and they each averaged 320 yards and 24 points for the season, are they evenly matched offenses? According to these two stats alone they are; but we don’t know anything about what the team went through to come to these numbers. That’s why I propose we start tracking weighted yards. Weighted yards will cut through the mystery and explain how many yards these teams DESERVED to finish the season with. How? Strength of schedule.

            Just one month ago the NFL Network had a show in which they released the schedules of all 32 NFL teams. Every football fan in the country seemed to be interested and all we heard about for the next 2 days was what teams had the hardest and easiest schedules. And then what? Nobody cares about strength of schedule until, well, until next year’s schedule release show. This is understandable; strength of schedule in the offseason really means nothing because teams that look good in September could be out of it in December and teams that look like contenders in August could be out of it by November. But strength of schedule in the regular season, which no one talks about, means a ton.

            Let’s pretend that the Falcons and Steelers were to matchup in the Superbowl last season (The Giants, the Broncos, and other 8 teams that made the playoffs had something better to do in this fictional world). The Falcons averaged 376.6 yards per game in the regular season while the Steelers averaged 372.3. So conventional wisdom would indicate that the Falcons had a slightly better offense, but how did they get here. We need to look at the strength of the defenses these teams played. To make this easier I have taken each team’s total yardage and turned it into a decimal, for example the league average in yards allowed per game is 347 so if a team allowed 173.5 yards per game they allowed .5 or half of the league average. Any number higher than one indicates that the team allowed above the league average in yards per game. The Falcons schedule looked like this:

Chicago
1.0103
Philadelphia
0.9368
Tampa Bay
1.1371
Seattle
0.9578
Green Bay
1.1867
Carolina
1.0887
Detroit
1.0599
BYE

Indianapolis
1.0694
New Orleans
1.0622
Tennessee
1.0238
Minnesota
1.0328
Houston
0.8237
Carolina
1.0887
Jacksonville
0.9024
New Orleans
1.0622
Tampa Bay
1.1371
AVG
1.036229

This may look confusing but when you average all these numbers out it means that the defenses the Falcons faced allowed, on average, 3.6% more yards per game than the average defense. This means that although the Falcons gained 376.6 yards per game, against an average defense they would be expected to gain only 362.9 yards per game. The Steelers schedule breaks down like this:

Baltimore
0.8330
Seattle
0.9578
Indianapolis
1.0694
Houston
0.8237
Tennessee
1.0238
Jacksonville
0.9024
Arizona
1.0238
New England
1.1853
Baltimore
0.8330
Cincinatti
0.9117
BYE

Kansas City
0.9610
Cincinatti
0.9117
Cleveland
0.9584
San Francisco
0.8886
St Louis
1.0333
Cleveland
0.9584
AVG
0.9547

This means that the defenses the Steelers faced allowed, on average, 4.5% less yards per game than the average defense. Had the Steelers faced an average defense they would be expected to gain 389.2 yards per game instead of the 372.3 that they gained against their much tougher schedule.

            So at initial glance these offenses are very similar with a slight edge going to the Falcons, but when we actually take into account how these numbers were earned it becomes clear that the Steelers were much better than their numbers would indicate and the Falcons weren’t quite as good. Now the numbers say that the Steelers gained 389.2 yards per game compared to the Falcons 362.9. This is a difference of 30 yards from what conventional stats would tell us, and any football fan knows that in a game of inches 30 yards can be as good as a mile.

            The basis of these stats can also be used to predict defensive performance by using the same calculations. They can also be used to predict how teams may fare against each other but I will get into that in a separate article, for now just remember that when two teams play each other yardage doesn’t tell the whole story.

           

Sunday, May 6, 2012

Why the 49ers were so good, the Rams were so bad, and neither should expect the same in 2012


            The 49ers came out of nowhere in 2011 and were one Ted Ginn injury away from playing in the Super Bowl. The Rams came into the season with high expectations and ended it tied for the worst record in the NFL. The difference? Well, talent obviously played a part, as did injuries (The Rams had to set the NFL record for cornerbacks on injured reserve), and coaching. But one of the biggest factors was just plain luck.

            One spot where the 49ers were lucky and the Rams were not was in a category of yards per point. This is not a statistic that is thrown around often (or ever as far as I know) but does reveal some very interesting things about the 49ers and Rams seasons. On average an NFL team scores 1 point for every 15.64 yards that they gain. So if the Rams gained 283.6 yards per game (which they did) they would be expected to score just over 18 points per game. They barely managed to score 12 points per game (12.1) that means they scored 1 point for every 23.4 yards! This was by far the worst in the NFL. The 49ers on the other hand averaged 310.9 yards per game. With an average ratio they would have scored just under 20 points per game, instead they scored 23.8 points per game (13.1 yards per point).

            On the defensive side of the ball the difference was just as striking. The Rams allowed 25.4 points per game and 358.4 yards per game. That is a point for every 14.1 yards, not a terrible number (an average team giving up the same amount of yardage would have allowed 22.9 points per game) but still below average. The 49ers allowed 14.3 points per game and 308.2 yards per game, in other words they allowed a league low 1 point for every 21.6 yards they gave up! An average NFL team would have given up 19.7 points per game with as many yards as the 49ers allowed.

            It may not seem like much at first glance, but based on these numbers the Rams gave away 8.5 points per game and the 49ers stole 9.3 points per game. This can’t be written off 100% as luck but numbers this extreme are guaranteed to level themselves out. The greatness of the 49ers defense and the terribleness of the Rams offense are both completely unsustainable.

            The other way in which the 49ers were lucky in 2012 (other than Alex Smith suddenly playing like the 1st overall pick in the draft) was turnovers. The 49ers had a turnover differential of +28! How huge of a jump was this? Well the 49ers had a -1 turnover differential in 2010. It would be unrealistic to expect the 49ers to have such a high turnover differential in 2012 and they will probably fall somewhere between the numbers of the past two years.

            Does all this mean I’m picking the Rams to finish above the 49ers in the NFC West this year? Well I’m not going to bet against a team that barely missed the Super Bowl and had a great offseason. I’m just saying don’t be surprised if the 49ers fall back to the pack and the Rams are in contention for a playoff spot.  
(All team statistics from NFL.com)

How to build an NFL team

What is the best way to build a team in the NFL right now? Let’s say you took over an expansion team in today’s NFL, How would you build them?

I’m sure most people would say the way to do it is to surround your quarterback with talent at the receiver and cornerback position and sling the ball around like Aaron Rodgers, Drew Brees, and Matthew Stafford. What would I do? I would start stocking up on big defensive linemen, bigger offensive lineman and a power running game. Is this outdated in today's NFL? Yes. Will this team be dominant in 5 years? YES.

The NFL is a passing league more than ever right now. But why? Rule changes favor the passing game, but rule changes have always favored the passing game. The best athletes on the field play wide receiver but that has always been the case. Receivers are getting bigger every year but so are cornerbacks. Quarterbacks are getting stronger every year but so are defensive linemen. Offenses are always getting more sophisticated but so are defenses. People have said that the NFL will be a passing league from now on. I disagree, I believe that the rise in passing is strictly temporary and will fall back to what it was pre-1990 within a few years. I believe that by 2016 we will be in a league that is dominated by the run for the first time in decades.

Passing yards per game have been rising somewhat consistently since 1990 with a few outliers.  The gap between 2010 and 2011 is no greater than the gap between 2008 and 2009 or 2006 and 2007. Attempts per game have also been on a semi-consistent rise (I have no idea what the hell was going on in 1995 but pro football reference theorizes it was because of the expansion causing dilution of talent). Rushing attempts per game have barely decreased over the same time span (27.8 in 1990 to 27.3 in 2011) so teams are simply getting more plays these days, due to a hurry up offense and the clock stopping after incomplete passes.

So why would anything stop this upward trend of the passing game? Interestingly in 2011, "the year of the quarterback", rushing yards per attempt were at an all time high. Why? Because teams are trying to stop the pass and shifting to defensive formations with more defensive backs

Formations with 5 defensive backs were used 19% of the time in 2011 more than double the 9% rate of just three years before. While formations with 6 defensive backs have not risen as significantly the pattern would indicate that soon teams will begin employing more 6 defensive back sets. It is also worth noting that the Super Bowl champion New York Giants and the team with the best regular season record the Green Bay Packers had 5 defensive backs on the field on 75% and 69% of their defensive snaps, number 1 and 2 in the NFL.

What a team should be doing right now is switching to a primarily nickel defense. If current trends continue, and they will, the base defense in the NFL will be the nickel by 2014. Passing windows will shrink. Defensive backs with good speed and not much size will be covering the field. Smart teams will expose this with bruising running games. Passing numbers will come down to earth, running numbers will skyrocket, and we will have the year of the running back

Or more likely -- The Decade of the Running Back