How Spread Offenses Are Killing NFL Offensive Lines

The NFL is evolving at breakneck speed. As more NFL offenses incorporate multi-WR sets and throw out of them more often, NFL passing yardage records are taking heavy casualties. Pass-catching tight ends are getting harder to distinguish from wide receivers. The "workhorse back" is becoming an endangered species; tailbacks are being integrated high-octane passing offenses.

It's all killing the offensive lines.

As ESPN's Ross Tucker notes, fans are turning up the heat on offensive lines. Most NFL fans are convinced their team's line is doing a poor job of protecting their quarterback. Tucker explains:

"If close to 75 percent of the fans in the NFL think their teams' offensive line stinks, maybe the problem isn't actually the offensive line but rather what they are being asked to do?"

According to Tucker, "The hardest task for most offensive linemen is blocking one-on-one in an obvious passing situation. I know it was for me."

It's not just that offenses are changing, Tucker says. "It's especially true when you consider that not only are defensive blitz schemes increasingly complex, teams are putting a tremendous focus on having four accomplished pass-rushers out there in every passing situation and often rotating players to keep them fresh."

Offensive line performance is notoriously difficult to quantify. Football Outsiders uses an "Adjusted Sack Rate" metric, but they adjust by normalizing for pass snaps and down-and-distance. If the fans think offensive line play is suffering because pass-happy offenses are hanging linemen out to dry, FO will normalize that effect right out of the data.

Another advanced pass protection metric is the New York Life Protection Index. Unfortunately, there are a couple problems with that one. First, it's proprietary, compiled by STATS, Inc. without transparency. Second, the teams whose quarterbacks throw the ball away invariably lead the rankings. In 2009, the Indianapolis Colts and New Orleans Saints finished first and third respectively despite both teams sifting through their rosters to find a half-decent left tackle.

The best source for year-over-year offensive line evaluation I could find is Pro Football Focus's grades.

This is the distribution of PFF team pass block grades for 2009, 2010 and 2011 to date. The X axis is standard deviation from the mean, and the Y axis is the number of teams who fall into the half-standard-deviation tiers. “-3.0” is three standard deviations below the mean, “0” is the mean and “+3.0” is three standard deviations above the mean.

The first thing that jumps out at you is the way the 2009 line appears to disappear. In fact, 2009 and 2010 had the exact same distribution above the mean: eight teams between the mean and one-half standard deviation above, six teams between +0.5 and +1, five teams between +1 and +1.5 and no teams two standard deviations or more above the mean. In both seasons, then 19 teams were graded above the mean.

In both seasons, there was a hearty group of “above average” pass blocking lines; the majority of NFL offensive lines were a little bit better than the mean. On the downside of those two slopes, the distributions are similar. They seesaw with a gap of two or three teams from -0.5 down to -2.5, where they each have one. Both years share an overall shape: a few awful teams, several bad teams, some “meh” teams, then most of the NFL is between “OK” to “good,” with just a few “pretty good” pass-blocking lines and no “very good” or “great” ones.

A quarter of the way through this year, a different shape is emerging. Only 16 teams are grading out above the median, meaning four fewer “good” or “pretty good” pass-blocking lines. The Tennessee Titans are that outlying bump at +2.5, an entire standard deviation above the second-best Buffalo Bills.

After that, though, it’s more bad news: Nine teams are at least 1.5 standard deviations below the mean, compared to four in 2010 and six in 2009. That’s 28 percent of the league’s offensive lines at “bad” or worse!

Now here’s the interesting bit. We see that so far in 2010, there are fewer relatively “good” pass-blocking lines and more relatively “bad” ones. But that’s only relative to each other in the same season. What about year-over-year?

PFF normalizes all of their grades, meaning these grades aren’t just the raw scores. The first season they graded (2008), they adjusted the grades so they averaged out to zero. In subsequent seasons, they’ve normalized their grades with the same factors as from 2008—meaning, grades from 2009 and 2010 and 2011 will compare directly to 2008 (and each other).

Look at 2009’s mean: -0.22, or almost exactly zero. This means that PFF’s raw pass-blocking grades (and in theory, league-wide pass-blocking performance) was almost identical from 2008 to 2009. But in 2010, that mean dropped to -18.56. In 2009, a team that graded out at -18.56 would have been binned in the “-0.5 to -1.0” tier! If we do an incredibly crude projection of this season’s grades (multiply by four), the average 2011 team will grade out at –24.99, very nearly a full standard deviation below 2009’s mean!

This implies that league-wide pass blocking performance has declined dramatically from recent norms. Not only has the distribution changed so that more teams are “bad” at pass blocking while fewer are “good,” the standards for “bad” and “good” are noticeably lower.

Here’s a better way of seeing the year-over-year change: the 2009 grades are an almost perfect expected distribution between extremes, norms, positives and negatives. The 2010 grades have a nearly-identical shape, just with an across-the-board decrease. The 2011 grades, though crudely projected, again reflect a change in distribution: There are far more bad-to-awful lines and far fewer decent-to-good ones.

PFF detractors will be quick to claim this as proof of flaws in their methodology; that’s certainly possible. But it dovetails perfectly with what Ross Tucker has observed: Teams are passing at a ridiculous rate and increasingly using tight ends and running backs as targets rather than blockers. They’re hanging their offensive linemen out to dry to spread the defense and the ball around the field—and it’s showing in both passing effectiveness, and pass protection grades.

Tucker said it best: "At a minimum, fans and media alike need to look at the number of teams unhappy with offensive line play and realize that maybe this is the new normal. If that is the standard of performance for more than half of the teams in the league, then that is, by definition, the average."

Perhaps this points to the next offensive trend in the NFL. As more and more teams struggle to keep their quarterbacks upright, struggle to control the ball and struggle to protect leads, perhaps the pendulum will swing back the other way.

Perhaps teams will return to the power run, pushing around overaggressive pass-rushing defensive lines and soft umbrella zones. Perhaps teams will return to using tight ends who play more like third tackles. Perhaps football's evolutionary clock will spin backwards, away from an aerial game played standing up and towards the rugby scrums which birthed it.

For now, though, NFL fans will have to get used to "bad" pass protection being the new "good."