By now, news of DeMarco Murray's exploits on the football fields have travelled to the furthest reaches of Cowboys Nation.
Comparisons with former Cowboys greats like Emmitt Smith and Tony Dorsett are being drawn left and right, many Cowboys fans are embroiled in a luxury debate about which Cowboys back should start and who should get more carries, and there's even emerging talk about Murray joining the list of potential Rookie of the Year candidates.
Somewhat overlooked in this discussion is the role the offensive line has played in Murray's emergence, so after the break, we take a closer look at the O-line contribution.
DeMarco Murray appreciation stats
Here's a breakdown of some stats from ESPN's Stats & Info blog that show just how remarkable Murray has been as a runner.
As the article notes, a lot of Murray’s success comes from his ability to get the tough yards. Murray’s 3.0 yards after contact is the best rate in the league, and is also an improvement on the 2.3 yards Felix Jones average.
To see just how much the blocking is contributing to Murray's overall numbers, we turn to our friends from Football Outsiders. FO have developed two specific metrics to evaluate blocking and rushing performance that we'll look at in the following.
Adjusted Line Yards:
Based on regression analysis, the Adjusted Line Yards (ALY) 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 4.33 yards after ten weeks in 2011].
ALY penalizes an offensive line when a runner is tackled for a loss by adding 20% on top of the negative yardage (e.g. a run for -5 yards is credited with -6 yards, or 120% of the original value). It also gives progressively less credit for long runs, simply because the contribution of the line, once the runner hits the open field, quickly approaches zero.
Therefore, 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 actual yardage and 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 at all.
Using Adjusted Line Yards, this is how the Cowboys offensive line performed so far this year, and how that compares to previous years:
|Year||Rank||Adj. Line Yards||RB Yards||NFL Avg|
|Wk 10, 2011||5||4.38||5.03||4.33|
Yes, you read that correctly, the Cowboys' O-line is a top five run-blocking unit. Coincidentally, FO ranks the O-line number four in pass blocking as well. I'm not sure there was anybody at the beginning of the season who predicted Cowboys would have a top five offensive line.
But what's perhaps even more remarkable is that through the first four weeks of the 2011 season, the Cowboys' O-line was ranked 25th in the league in ALY. Moving up to number five only five games later is a significant change in performance, that also coincides with Murray's emergence as well as a healthy Tony Fiammetta and Montrae Holland getting starts.
At this point, the Cowboys' offensive line is clearing a path for significant chunks of yardage for its running backs. DeMarco Murray is adding significant extra yardage after contact. Taken together, this has resulted in a Cowboys running game that is turning heads across the league.
The running backs
You cannot evaluate running backs in isolation from their O-line. So while you can't completely separate the effect the two position groups have on each other, you can approximate it by looking at the relationship between Adjusted Line Yards and Running Back Yards, which are the standard NFL numbers.
Per the table above, the Cowboys’ running backs are gaining 5.03 yards a pop in 2011, the fourth best value in the league behind the Bills (5.44), Eagles (5.16) and Raiders (5.15). That's pretty impressive any way you look at it.
If you deduct the the Adjusted Line Yards from the Running Back Yards you'll get a good measure of how the running backs performed relative to the line, because by taking away the contribution of the offensive line, be it good or bad, you'll get a measure of how good a running game a team has. The table below does that calculation for the top five and bottom five teams in 2010.
|Running Back Yards minus Adjusted Line Yards, 2011|
|Rank||Team||RBY - ALY|
Despite a very slow start to the season, the Cowboys' running game now ranks as one of the top units in the league. A lot of the credit must go to the offensive line and their blocking. But an equal amount of credit must go to DeMarco Murray, who has brought an almost unprecedented level of excitement to the Cowboys' ground game.
Football Outsiders concur. In their DVOA rankings, Murray is ranked as the second best running back in the league.