Lito Sheppard, Sabermetrics Martyr
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As advanced football statistics become part of the everyday vocabulary, you can bet that they'll be used more and more in contract negotiations on both sides of the table. Defensive stats have lagged behind (sacks weren't even recorded until 1982, leaving generations of pass rushers deprived of historical comparison), but a recent comment made by Philadelphia Eagles owner Jeff Lurie about cornerback Lito Sheppard proved that more advanced numbers have infiltrated at least one front office.
At a state-of-the-team address in early August, Lurie was asked about Sheppard's dissatisfaction with his situation after the team signed ex-Patriots cornerback Asante Samuel to an enormous contract. "I will say that I'm very hopeful that Lito will have a terrific season . . . (that he's) got great playmaking ability and certainly a lower YPA," Lurie told the assembled media. It was the YPA (Yards Per Attempt) comment that caught everyone's attention, and Sheppard did indeed suffer in this category. What's more revealing is that the Eagles' front office had been crunching some new numbers, and they're not the only team doing so.
YPA, which was probably first tracked by STATS, Inc., reveals how many yards a defensive player gives up per passing attempt in which he is the listed target. It's a neat addition to the old chestnuts, interceptions and passes defensed. But as Sheldon Brown, Sheppard's teammate, noted in response to Lurie's comments, YPA isn't the end-all, either.
"If a guy runs deep and the safety blew the coverage and now I'm chasing him, now it's my YPA? I want to meet the guy who's figuring this out," Brown told Philly.com. "I would like to talk to him about the defensive scheme we're running."
And that's just it. We have an indicator of how many yards a defender allows, but we haven't accounted for scheme, or safety help, or situation, or opponent. YPA is an interesting mileage marker on the Stat Highway. We need to head further down the road with a few new numbers. We know that Sheppard finished 66th in Average Yards per Pass (PaYd), the Football Outsiders version of the stat) with 8.5, but what does that mean?
Over the last few years, Football Outsiders has assembled play-by-play and game-charting data to get a little closer to the truth. When it comes to pass defenders, there are now more ways to rate them:
Targets: the number of times our game charters listed a player in coverage;
Target Percentage: the number of plays a player was targeted divided by the total number of charted passes against his defense;
Distance: the average distance in the air beyond the line of scrimmage of all passes targeted at a defender;
Passes Defensed: our count of the NFL stat, which differs slightly in the way we track it; and
Success Rate: The percentage of plays targeting a player in which the offense did not have a successful play. This includes incomplete passes, and completions which do not meet FO's standard for success: 45 percent of needed yards on first down, 60 percent in second down, and 100 percent on third or fourth down.
Situational stats are important, because they give us a better view of real effectiveness. In 2007, Sheppard's Success Rate was 36%, ranked 78th and one of the NFL's worst. But this tells us not only that Sheppard gave up yardage, but how.
There are aspects of defensive back play that remain uncharted, but their absence speaks volumes. In particular, the fact that the best DBs are often the least targeted. This was proven in 2007, when Oakland's Nnamdi Asomugha -- quite possibly the game's greatest at his position -- was thrown at so infrequently, we had to change the baseline for targets just to include him with the NFL's other 63 starting cornerbacks. If this sounds like Deion Sanders' ability to shut down half the field with his presence, it should.
Sheppard, on the other hand, was targeted 20 percent of the time -- higher than any other Eagles cornerback. The combination of Sheppard and William James was targeted 44 percent of the time, while Sheldon Brown's area on the other side was targeted 30 percent -- the highest discrepancy between left and right for any team other than Oakland. Must be that Asomugha guy again...
Clearly, when additional game-intensive numbers are added, we're talking about bigger differences between players than simpler stats can illustrate. Going forward, that's why teams will be well-served by looking at the big picture.
By
Doug Farrar
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September 16, 2008; 12:59 AM ET
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