Rewind'10: 'Stop Rate' against the pass

Monday, June 27, 2011

By Kevin Seifert

As June winds down into what we hope is a more exciting July, our friends at Football Outsiders continue to offer up unique analysis of your favorite NFC North players. Recently, Aaron Schatz published a number of tables that help us make a dent in the relationship between quality pass defense and tackle numbers.


Vikings cornerback Antoine Winfield was one of the NFL's most effective pass defenders last season.
(Really. I know we've debated this before. At least a few of us. Ok, maybe just me. But it's real and it's a debate so let's fiiiiiiiiiiiiiiiiiight!)

Typically, a cornerback with high tackle totals is associated with poor pass defense. The same goes for linebackers and safeties, to a lesser extent. The idea: Either quarterbacks avoid the best pass defenders, or the best pass defenders prevent more than their share of completions on balls thrown their way.

But that's not always the case, obviously. To that end, Football Outsiders has developed a "Stop Rate," which is the percentage of plays "that prevent a successful play by the offense, defined as 45% of needed yards on first down, 60% of needed yards on second down, and 100% of needed yards on third or fourth down." In other words, a "stop" is a successful defensive play, even if it results in a yardage gain by the offense.

Schatz offers a number of applicable individual marks under this category. The NFC North highlights:
Not surprisingly, Minnesota Vikings cornerback Antoine Winfield, an elite tackler, tied for the NFL lead with 28 stops last season. His Stop Rate of 41 percent ranked No. 5 in the NFL. So even though he had a high number of tackles on passing plays last season (68), it's wrong to call Winfield anything close to a poor pass defender.
On the other hand, Chicago Bears cornerback Charles Tillman had 64 tackles on pass plays last season with only 11 "stops." That gave him a Stop Rate of 17 percent.
Bears nickel man D.J. Moore had 11 stops on 28 tackles against pass plays, a Stop Rate of 38 percent that ranked him No. 6 among NFL cornerbacks. Moore finished tied with Green Bay Packers cornerback Charles Woodson, whose tackling we often overlook. Woodson had 18 stops on 47 tackles against the pass.
Packers safety Charlie Peprah had the best Stop Rate (44 percent) among safeties. Vikings safety Madieu Williams had the ninth-worst (6 percent). Those of us who watched both teams closely last season shouldn't be surprised.
Vikings linebacker Chad Greenway had 61 tackles against the pass last season, second most among NFL linebackers. He had 19 stops for a 31 percent Stop Rate. So there is some, but not much, room to question the quality of Greenway's coverage.
Detroit Lions linebacker DeAndre Levy had the fifth-lowest Stop Rate (24 percent) among NFL linebackers. Levy has consistently appeared on Football Outsiders' highest missed-tackle rate, but I'm not sure these two categories are related.

I'd rather watch and make my own determinations than to use these esoteric analyses to determine who is and who isn't doing their job. This is just another in a long list of articles where the author arbitrarily sets his own set of standards with which to analyze players. I just don't buy into these things like others may do.

Yawn, yet another boring article about assymetric analyses on stuff that can't possibly be quantified by empirical study. Seifert basically made Charles Tillman look like a dog in this article, yet "Peanut" is still one of the most respect CB in the game. He does everything that a Lovie Smith corner is asked to do: he more than adequately guards his zone, he makes tackles, and he creates turnovers. Antoine Winfield plays in a man-to-man defense and is asked to blanket his receiver. To me, there is no comparison because each man's job description is different from the other.

This mentions nothing about how the amount of pressure applied by the pass rush factors in to the equation ; which probably makes a cb's stop % higher if the rush is good . If corners are worried bout getting burned ( if the d-line sux ) naturally they are going to be less aggressive and play more of a bend don't break style ( which may not accurately reflect how good they are / aren't ).

Quote:

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Originally Posted by Blue Horse-shoe

This mentions nothing about how the amount of pressure applied by the pass rush factors in to the equation ; which probably makes a cb's stop % higher if the rush is good . If corners are worried bout getting burned ( if the d-line sux ) naturally they are going to be less aggressive and play more of a bend don't break style ( which may not accurately reflect how good they are / aren't ).

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This last year's defensive line met with some mixed results. On one hand, it was the second best team in the league against the run. On the other hand, it couldn't sack its way out of a woman's bed in a whorehouse if it wanted to. It eventually got to where we were having to give up huge chunks of yards between the two 20 yard lines because we weren't getting any help from the defensive line in terms of a pass rush. Thankfully, we got help in the draft in Stephen Paea. I really think he's going to be good. His presence, should he blossom into a solid three-technique, will help out a lot with the woes of the pass defense, which I think was only like 21st in the league in yards given up in '10.

I guess we can come to the logical conclusion then that this analysis "ain't worth $hit" right? Somethings do lend themselves to a reasonable statistical analysis but some of the stuff we've seen this year is a way out reach IMO. This is one of them.