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Offensive Linemen are Just Not That Into You

offensiveline

Really the title should read “you’re just not that into them” but then I couldn’t reference a 2009 movie I’ve seen bits and pieces of on TV late at night. Anyway, now I’m going to try to at least start to quantify the effects of offensive lines on running games and then try to draw a bit of a conclusion from my past few articles.

Let’s Talk About Running 

Alright, so here’s a problem: how do you separate a running back from his line in the running game? I don’t really know, but the good folks over at Football Outsiders took a shot at it and they call it Adjusted Line Yards (ALY). One problem with ALY is that running backs definitely do affect yards per carry, even in the first five yards. For instance, if you needed two yards for a first down, I don’t think I need to reference a metric to convince you Marshawn Lynch is better suited for that particular task than Chris Johnson. Anyway, I couldn’t think of any reason offensive lines would help a runner break tackles, so I looked at missed tackles forced/attempt for each team’s two leading rushers in attempts and found that it explained 17% of the variance in a teams’ Adjusted Line Yards. I then looked at what you would expect a teams ALY to be based solely on missed tackles forced by the back and subtracted it from F.O.s ALY Metric to get a (relatively) RB independent version of ALY, which I call Re-Adjusted Line Yards (I call it that because I think the name is funny and am like 99% sure it won’t catch on anyway). If anyone is curious, Baltimore and Jacksonville are the only two teams more than half a yard below average by this metric and San Diego, New England, and Green Bay are the only teams half a yard above average. Intuitively you don’t think of New England and Green Bay as great run blocking teams because they have a reputation for having elite quarterback play, but when you think about it, between Stevan Ridley (meh), Legarette Blount (meh), and Brandon Bolden (meh) all having a ton of success in the New England backfield, it’s kinda hard to think they wouldn’t have awesome run blocking. Same for Green Bay, I mean, yeah, Eddie Lacy was a highish pick, but when he was out James Starks wasted no time tearing up the league.

Putting it All Together 

So lets take my past three articles and do a back of the napkin calculation of the value of an offensive line.

In my sample of QB Agnostic Offensive Line Score1 a bottom 10% unit gives up about 5% more pressures than an average unit and a top 10% unit gives up about 5% fewer pressures than an average unit. So assuming 600 drop backs, a bottom 10% unit would face 60 more pressured snaps than a top 10% pass blocking unit. Of those 60 pressures 17.5% would turn into sacks for 10.5 extra sacks. In addition, hurried passes are completed 20% less often than unhurried passes, so of the 49.5 pressures that don’t end in sacks, we would expect about 10 fewer completions for the bottom 10% unit.

From a running standpoint, the difference between the third best and third worst unit last year in terms of Re-Adjusted Line Yard is 0.9 yards/carry. So if you could go from having an offensive line that is bottom 10% in the NFL to a top 10% line (pretend run blocking and pass blocking are perfectly correlated, I know they aren’t) you’re looking at about a 1.5% increase in completion percentage, 0.6 fewer sacks a game, and an extra 0.9 yards per carry. For a unit consisting of five different starters each drawing a separate salary, that seems pretty shitty right? I mean we’d need to pin down the effect one star player would have on an offensive line, but you don’t really see the bare ingredients of an argument supporting using top 5 picks on offensive linemen here I don’t think.

  1. wow, that name sucks, that’s why you don’t write at 2 a.m. I’m changing the name to Quarterback Independent Blocking (QIB)   (back)

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