Matthew Stafford’s Day(s) Off

>> 6.18.2010

As many outlets have reported, the Lions have been docked two days’ worth of OTA practices for CBA violations.  Specifically, the Lions’ OTA practices exceeded allowed limits for tempo and contact.  This might sound familiar—indeed, the Lions lost two OTA days due to fiesty practices back in 2006, as well. Guessing which player had filed the NFLPA grievance turned into a favorite parlor game for Lions fans, bloggers, and newsmedia.

Ultimately, reported that Marcus Bell had blown the whistle on Rod Marinelli and the Lions coaches.*  At the time, most observers belonged to one of two camps:

  • “If there’s dissension in the ranks, Marinelli’s ‘Pound the Rock’ message is already falling on deaf ears.  ”
  • “GOOD!  Those lazy goldbrickers need to be whipped into shape!  Let ‘em whine, the wheat will be separated from the chaff.”

Of course, Marinelli was trying to make an impact.  He was touting himself as a hard worker, a motivator who demanded his player be motivated.  His mission was to cut out the deadwood and have 53 rowers all swinging their invisible pickaxes in harmony, or something.  That all 53 weren’t buying in right off the bat was troubling; wasn’t Rod supposed to be able to get a cat to want to run through a brick wall?  It seemed an ill omen for building a truly cohesive unit.

So, what are we to make of this?  Jim Schwartz, the Grandmaster?  The one whose intellectual approach and meticulous preparation made his name legend amongst the football dorks of the Internet?  How could he be so careless as to violate the rules, even as the Ravens, Raiders, and Jaguars had already been caught?  Indeed, Paula Pasche of the Oakland Press just finished blogging about how Schwartz is too smart, and too careful, to violate the OTA guidelines (and contradicting PFT’s fingering of Marcus Bell in the process).

Nick Cotsonika also just posted a piece explaining the creative lengths Schwartz and company are going to stay on the right side of the law.  Apparently, these lengths weren’t creative enough—or, possibly, were they too creative?  Did a player, or player, decide that flipping and catching a tire was the football equivalent of cruel and unusual punishment? 

More importantly, what does this mean for the Lions and their team chemistry?  This isn’t a lazy, underperforming group going into their first practices under a hardnosed taskmaster.  This is a talented young team, handpicked by Mayhew and Schwartz for their New Era Of Awesome Lions.  Who’s not buying in?  Who’s so disgruntled with Schwartz that they’d go to the NFLPA?  Could this be a sign of the upcoming CBA-pocalypse?  Is this whistleblowing the first shot in the upcoming labor war between Lions players and Lions management?

No.  You see, in the wake of years of tacit, wink-nod slides from non-contact, to kind of a little contact, to mostly-full-speed OTAs, the NFLPA is now reviewing tapes of OTAs.  Apparently, the tempo and contact crossed the line.  There was no whistleblowing.  There is no dissent.  The Grandmaster’s plan is still intact, ready to be executed . . . he’ll just have fewer days to tell the players how to do it.

*UPDATE: At the time of writing, I wasn’t aware that PFT’s report wasn’t the final word on the issue.  Corrected the language to reflect this.


Guest Article: Detroit Lions Fantasy Preview at

>> 6.16.2010

Anyone who’s a fantasy sports enthusiast, as I am, has spent some time over at  They blend great fantasy info and advice with snappy writing and actual humor.  I was psyched when Chet from Razzball reached out to me, and asked if  I’d be willing to answer some questions about the Lions’ fantasy outlook for 2010.

Even if I weren’t flattered to be asked—I was—I was thrilled at the notion that someone thought the Lions might be relevant to fantasy football in 2010!  So, I gladly answered Chet’s very-well-informed questions.  Please, check it out here:


The Defensive Line and the Secondary, Part II

>> 6.14.2010

When I first delved into the connections between pass rush and pass defense, I came away conclusions fueled partly by data, and partly by ignorance.  They were:

  • We have found that there is no inverse correlation between that pass rush effectiveness and passing effectiveness; on plays where a sack does not occur, per-play pass yardage is unaffected.
  • We have found that there is no inverse correlation between interception rate and passing effectiveness; on plays where an interception does not occur, per-play pass yardage is unaffected.
  • These may have been exaggerations.  Commenters, emailers, and strangers on the street have since filled me in.  The correlation coefficients looked dismissible to my amateur eyes, but weren’t—not entirely, anyway.  There was a –.068 correlation coefficient between “dropbacks per sack” and “raw yards per attempt”.  Essentially zero, I thought, but it’s closer to –.1 than to zero—and that’s more than nothing.  Not much more, but more.

    The correlation coefficient between "attempts per interception" and "yards per attempt" was –.091.  That’s still only approaching .1; a weak correlation at best.  Still, my two statements above aren’t entirely accurate.  Over the past 20 years of NFL data, there has been a very mild inverse correlation between sacks, and pass effectiveness on non-sack downs (and the same goes for INTs).

    This all implies that the pass rush might indeed affect offense even when it doesn’t hit home—but I couldn’t prove it with the data I had.  I’d been working with the 50,000-foot-view: year-over-year leaguewide NFL trends; he low resolution of this data may have blurred the very effects I’m hoping to measure.

    As I said in my “parallel efforts” post last week, the Mathlete, of MGoBlog fame, did some of that further research.  As the Mathlete compared sacks, picks, and overall performance, he found:

    Not entirely surprisingly, the better a defense is at producing sacks and interceptions, the better it is on downs where neither occur. For every point per game that a defense generates due to sacks, the overall pass rush generates 1.2 ppg of additional value. Interceptions are also powerful, but not as much so. Each ppg of value a defense generates through interceptions is worth 0.9 ppg of additional value.

    This relies on “expected points,” here explained by Brian Burke of Advanced NFL Stats.  EP is a way to recognize the reality that four yards gained on 3rd-and-3 are not nearly as valuable as four yards gained on 3rd-and-8.  By finding the historical likelihood of scoring on a given down and distance from a given field position, Burke has created baseline EP values.  By finding the difference between the EP values from before a play to that play, you can gauge what that play is worth (in EP Added, or EPA).

    Using EP allowed the Mathlete to quantify exactly what sacks—and the associated pass rush on non-sack downs—are worth.

    From 2006-2009 in games between two D1 teams in competitive game situations (the “universe” for this and most of my analysis) the average defensive unit produced 2.3 ppg worth of sacks and 2.0 ppg worth of interceptions.

    So, an average defense produced 2.3 ppg worth of sacks, and gained 2.76 ppg worth of “footsteps effect” from the pass rush.  Likewise,  the average defense snared 2.0 ppg worth of interceptions, and 1.8 ppg worth of “dink-and-dunk effect”.  Mathlete concluded that all he found was the dog wagging the tail: sacks and picks are merely indicators of good defensive performance, not the other way around.

    However, this is all still limited to sacks, and attempting to derive the “cringe effect” on non-sack plays.  However, I’ve pulled down data from They use film review to grade individual performances, as well as capture unofficial or untracked stats—like QB hits, and QB pressures.  Rather than attempt to measure the size of the tyrannosaur by the size of the ripples in the water cup, I’ll look at the actual data.

    The data I’m using is PFF’s player data for the 2009 season, aggregated into team numbers.  A caveat, these numbers do vary from the official NFL totals, especially with subjective stats like sacks, half-sacks, and tackles.  From what I’ve seen, the differences are small, but it’s worth getting out there.  Anyway, the first order of business: test my assumption that pressures correlate with sacks.


    Result?  “Yes,” but not as strongly as I’d assumed.  The correlation coefficient was .584, quite strong.  But as an anonymous commenter noted:

    One of the best indicators of nature of the relationship is the effect size calculation. You can obtain an effect size by squaring your correlation coefficient. This will tell you the amount of variability the variables contribute to each other. There's a lot of noise in NFL data so an effect size will tell you how much unique data is explained by the correlation alone.

    Rule of thumb for effect sizes: small .2; medium .5; large .8

    The effect size here is displayed in that graph as R-squared: 0.3413.  It’s far from one-to-one, but it’s safe to say that teams that get lots of pressures tend to get lots of sacks, and vice-versa.  For what it’s worth, the best “finishers” are the Redskins, getting 43 sacks to 109 pressures.  For academics’ sake, the Falcons were the other way around: 160 pressures to only 31 sacks.  The Lions were . . . well, terrible: 23 sacks, and 101 pressures.

    Next up, let's take that “hit” and “pressure” data out for a spin:


    This is the total yards per attempt allowed, regressed against the percentage of dropbacks where “pass rush” was generated.  Dropbacks are “attempts + sacks”, and I’m dividing that number by cumulative sacks, hits, and pressures.  The resulting correlation is weak, –0.152, and when squared to get the effect size, it’s a negligible .0232

    So, once again, we’re seeing no real connection between pressure and good pass defense.  You see the most interesting data point?  Yeah, that one—the one where they’re allowing three-quarters of a yard less per pass attempt than the 2nd-best team.  That’s the New York Jets; they allowed a miniscule 4.91 yards per pass attempt, while finishing 19th in PFF-scored sacks, and 9th in per-dropback “pass rush” rate.  So, the Jets had a good pass rush, but nothing that correlates to the incredible per-play passing effectiveness seen here.

    Secondly, my eyes were drawn to the third-rightmost data point, and how we’d have to scrape it off the Yards-per-attempt ceiling.  That would be the Cleveland Browns, whose 47 sacks, 42 QB hits, and 139 pressures generated pressure on 42.93% of dropbacks.  That pass rush rate is third-best in the NFL, behind only Dallas (46.91%) and Minnesota (44.77%).  Yet, Cleveland’s pass D was flat terrible: it allowed 7.44 yards per attempt, ahead of only Oakland, St. Louis, Miami, and, yes Detroit (7.80). 

    Things are not looking great for our thesis.  If the Lions improved their 2009 per-dropback pass rush rate to match Cleveland’s, from 27.85% to 42.93%, we’d certainly expect a better improvement in allowed Y/A than 7.80 to 7.44.

    Last time, passes defensed were to coverage what sacks were to pass rush; I presumed that in years where passes defensed were up, “coverage” was better.  In this case, though, I have Pro Football Focus’s “thrown at” and “reception allowed” figures.  Again, let’s dispense with trying to derive the whole picture from one rare subset of outcomes.  FYI: Total TAs don’t equal attempts, and total receptions allowed don’t equal total receptions.  I presume the discrepancies are from uncatchable passes, screen and swing passes that aren’t thrown “into coverage”.

    I’ll divide total per-team receptions allowed by total per-team TAs to get a per-team Percent Caught, as PFF does on a per-player basis.  This should be an actual measurement of the quality of pass coverage.  Let’s regress it against Y/A:


    Bingo.  There’s as strong of a correlation between percent of catches allowed by coverage and yards-per-attempt, as there is between pressures and sacks.  Oh, and who’s that team with the astonishingly low percent-caught, and correlatedly low Y/A?  Yup, it’s the Jets.  The evidence is mounting: pass rush doesn’t equal pass defense, pass defense equals pass defense.

    But, that’s not the whole story, is it? After all, isn’t the magic of a 4-3 defensive line supposed to be that it can generate pressure without a compromising coverage?  Won’t there be great improvement in a 4-3 that generates pass rush from the line, without having to blitz linebackers and DBs?  Stay tuned for the next exciting adventure!


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