As we've learned the hard way this season, the offensive line may be the most important part of your football team. It's no surprise that the phrase 'building from the inside out' is often used when putting together a football team: The gridiron battle is won or lost at the line of scrimmage, and the offensive line is the lynch pin, literally underpinning the success of a team's offense.
Offensive linemen get noticed only when they make mistakes, they're the key to moving the ball through the air or on the ground yet their stats are largely invisible. So how can you judge the performance of an offensive line? Evaluating the performance of an offensive line is not an easy undertaking, simply because success is often only measured by what didn't happen: the quarterback was not sacked and the running back was not stuffed in the backfield. There aren’t a lot of stats out there that will help you tell a good offensive line from a bad one.
But there are two models out there that do measure offensive line performance: BTB favorite Brian Burke of advancednflstats.com just came up with a new approach which ranks the Cowboys O-line 12th. Another favorite of ours, Football Outsiders (FO), rank the Cowboys O-line 20th. The FO data includes the Jaguars game, Burke's doesn't. After the break, we take a closer look at what the FO data has to say about our run blocking game.
Football Outsiders have developed a couple of advanced metrics that evaluate offensive line performance based on a variety of factors. The goal of the offensive line in the running game is to give running backs the time and space to produce their numbers. Let’s see how the Cowboys O-line fared so far in 2010 according to the FO metrics.
FO have their own metrics and their own terminology, and I’ve used their definitions to preface each of the statistical categories we’ll walk through below.
Adjusted Line Yards:
Based on regression analysis, the Adjusted Line Yards formula takes all running back carries and assigns responsibility to the offensive line based on the following percentages:
Losses: 120% value
0-4 Yards: 100% value
5-10 Yards: 50% value
11+ Yards: 0% value
These numbers are then adjusted based on down, distance, situation, opponent, and the difference in rushing average between shotgun compared to standard formations. Finally, we normalize the numbers so that the league average for Adjusted Line Yards per carry is the same as the league average for RB yards per carry [which is 4.29 yards].
What these numbers mean is that the offensive line is penalized for losses (a run for -5 yards is credited with -6 yards) and gets progressively less credit for a long run: The first four yards of a run are fully credited, the next six yards (the running back hits the second level between 5 and 10 yards out) are only credited with half the yardage, for all yardage beyond the 10 yard line (the running back is now in the open field) the offensive line doesn’t get any credit whatsoever. This makes sense because you don’t often see offensive linemen blocking ten yards down the field for a running back – and Doug Free's downfield block on Felix Jones' touchdown run against the Eagles last year is the exception that proves the rule.
Using Adjusted Line Yards, this is how the Cowboys offensive line performed in 2009:
||Rank||Adj. Line Yards||RB Yards||NFL Avg|
So the run blocking performance of the O-line has dropped significantly versus last year. No big shocker there, and some might say that we didn't need any stats to tell us that. Fair enough, but bear with me.
Think of the Adjusted Line yards as follows: On average, the Cowboys offensive line cleared the path for 3.91 yards per run for their running backs. That ranks the line only 20th in the league. The adjusted line yards are down by a little over half a yard. Doesn't seem like all that much, but if they had kept the 4.47 average from last year, they'd be ranked 5th this year.
The next column in the table above are running back yards. FO define these as:
Yards per carry by that team's running backs, according to standard NFL numbers.
The Cowboys’ running backs gained 3.58 yards in running back yards so far this year, the fourth worst value in the league. This is a drop of almost 1.5 yards per run versus last year. Not good by any measure.
If you deduct the the Adjusted Line Yards from the Running Back Yards you'll get a good measure of how the running backs are performing relative to the line, because by taking away the contribution of an offensive line, be it good or bad, you'll get a measure of how good a running game a team has. And this is where you could start to really worry. The table below does that calculation for the top five and bottom five teams this year.
Running Back Yards minus Adjusted Line Yards
|Top seven Teams
||Bottom seven Teams
The Cowboys are ranked 29th in the league in this measure. Marion Barber and Felix Jones combined to gain 0.33 yards on average less than the offensive line provided.
So what does this mean? You take an average to bad O-line, pair it with two backs who have apparently both forgotten how to run and you have a running game that stinks to high heaven. Let me put it differently. If our running backs were running at the same clip as last year (+0.52 yards better than the O-line) they'd average 0.85 yards more per run than this year.
In summary: The O-line performance has declined by 0.56 yards per run versus last year. The RB's have declined by 0.85 yards versus last year relative to the O-line. At first glance it would seem that the decline in the Cowboys' overall run game this year is more a result of bad running than bad blocking.
But what sounds more likely to you: that the O-line performance has suffered or that our running backs capabilities have declined? Perhaps the Cowboys running backs are simply missing a couple of long runs that would 'pad' their stats?
In the second part of this mini-series, we’ll look at how the offensive line has performed on short and long runs, and in the third and final part we’ll look at how well the Cowboys ran the ball in different directions.