Tony Romo needs time to get through his reads, Miles Austin and Jason Witten need time to get down the field and get open, and the running backs need holes to charge through. Without an efficient offensive line, it becomes very difficult to move the football, and even the best offensive players can struggle to produce without effective pass protection or holes to run through.
The offensive line is key to moving the ball, yet evaluating the performance of an offensive line in pass protection is not an easy undertaking, simply because success is mostly only measured by what didn't happen: the quarterback was not sacked.
Traditionally, the O-Line's pass protection performance is measured by number of sacks given up. The Cowboys allowed 34 last season and ranked a joint 14th in the NFL. Today we look at how Footballoutsiders.com (FO) evaluate the O-Line performance and look the effect that blitzes have had on the sack rate last season.
Football Outsiders Sack Rank:
FO have some of the most advanced football metrics publicly available. Perhaps their O-Line rankings can shed a little more light on how well the Cowboys O-Line performed. FO have developed their own metric to evaluate an O-Line:
Adjusted Sack Rate (ASR)/Sack Rate: Sack Rate represents sacks divided by pass plays, which include passes, sacks, and aborted snaps. It is a better measure of pass blocking than total sacks because it takes into account how often an offense passes the ball. Adjusted Sack Rate adds adjustments for opponent quality, as well as down and distance (sacks are more common on third down, especially third-and-long)
What this means is that the Sack Rank percentage will give us the adjusted percentage of how often a sack occurs. To better understand this, let's look at the two New York teams: The Giants gave up 32 sacks, the Jets only 30. Sound pretty much the same, right? Well, consider that the Giants had 574 drop backs (pass attempts + sacks) and got sacked on 5.6% of those dropbacks, while the Jets had 423 drop backs and got sacked on 7.1% of those dropbacks.
These numbers make a pretty compelling case that while the absolute number of sacks given up slightly favors the Jets, there is little doubt that the Giants O-Line performed much better. The number of drop backs is just one factor to consider as you look at sacks, but you can easily see that number of sacks by itself is not a truly meaningful measure.
Using the FO Sack Rank, this is how the Cowboys offensive line performed in 2009:
||Rank||Sacks||Adj. Sack Rate||NFL Avg|
Ok, so the Cowboys O-line ranks 16th according to FO. That's not too far off the 14th rank in terms of absolute sacks allowed. But as we saw in the first post in this pass protection series, adding the context of 'sacks by direction' already added a level of detail to these absolute numbers that helped form a much clearer picture of the performance of the Cowboys' O-Line in pass protection. Now let's look at blitzes.
Blitzes and pass protection
For the Cowboys, the issue with blitzing pass rushers was more than just the inability of receivers to get open.
The delayed blitz was something like the Achilles heel of the offense last season. A defender would simply delay the blitz for a moment until all of the Cowboys were engaged in a block, and then shoot the gaps with relative impunity. Romo hardly stood a chance.
Identifying the correct blocks. Generally, the rules of the blitz suggest that at the line of scrimmage, the QB calls out who needs to be blocked and sets the protection against what he sees. The QB also has to account for the outside blitzer, and get rid of the ball fast enough to avoid the sack. I have no statistical evidence for this but some of the issues must stem from not identifying and then blocking the blitzing defender successfully.
Blocking the right guy. Bringing more rushers than blockers always means the linemen, RBs, TEs and whoever else is left in to block need to identify the right guy to block. As a rule, you block from the inside out. Where that didn't happen, bad things followed.
In all situations, Romo has to get the ball out, and quickly. But if nobody is open, Romo's uncanny elusiveness notwithstanding, at the end of the day it may be better to take the sack than to give up a fumble or an interception.
In fact, an argument can be made that the overall number of sacks is slightly inflated by Tony Romo making just that choice. BTB member ImpactNate argued the point convincingly in a fanpost last year (Way To Take That Sack, Tony Romo):
Romo did the smart thing last night...he took the sack, protected the ball, minimized the damage and came back for another play or series.
O-Line: Te absolvo
In part one of this series, we saw that the Cowboys allowed a disproportionate amount of 'long sacks'. Today we saw that the 'Boys were particularly susceptible to sacks on blitzes. In both cases, the sacks incurred are more indicative of a team-wide issue than of a specific O-line issue, and the 34 sack tally is an inaccurate reflection of how the O-line performed in 2009. In the next and final installment of this series, we'll look at individual players.
The good, the bad and the ugly: Sacks by defensive formation, 2009 (click column header to sort)
|Team||Total||Blitz||Non-Blitz||Blitz in % of dropbacks|