The NC State defense and turnovers forced
Greensboro News-Record writer Jim Young wonders about NC State's defense:
The Wolfpack finished the 2004 season ranked No. 1 nationally in total yardage yielded -- just 221.4 yards a game -- yet was 105th in turnovers forced -- just 15 in 11 games.
Which statistic is the lie? Which is the truth? Was the State defense a unit that suffocated opposing offenses for 60 minutes each game? Or was it a group of players who never quite made the big play at just the right time?
There's one reason why I don't completely trust the team statistics that are widely used today: many include some inherent biases (some more than others). Total defense measures pure yards allowed, but if your offense can't move the ball and/or turns it over a lot (there's something familiar sounding about that...), your opponents may be starting a lot of drives with a short field. Except in extreme cases, however, I'd guess that field position probably evens out over the course of the year, which is why I prefer total defense to scoring defense
Scoring defense is biased by turnovers made by the offense. It's hard to blame your defense for a pick six thrown by your quarterback (yet these TDs are counted when scoring def is calculated), or an opponent's drive that begins inside your red zone thanks to an untimely cough up.
Are they generally good indicators for aptitude? Definitely. But they aren't as useful once you get away from the margins...
The article goes on:
The widely held belief is that interception numbers are higher for teams that play zone defense, where players patrolling a certain area have a much easier time chasing down errant throws than do defensive backs who are locked in man-to-man coverage.
So why play so much man-to-man press coverage?
"The flip side of that is you're going to get a lot more sacks," Davis said. "When you're on the line of scrimmage, pressing, you're going to slow everything up. That quarterback's timing is going to be off."
In other words, while Davis and his defensive backfield mates are fasting (only nine interceptions last season), the defensive linemen are feasting (33 sacks, including 10 against Virginia Tech). One stat suffers as another blossoms.
I'm not buying it. I've taken a look at NC State's defensive numbers under Chuck Amato (since 2000), and I don't see a lot of support for the notion that more sacks means fewer INTs. But I'll get back to that in a minute. First, see the table below, which lists turnovers forced (national rank in parenthesis), turnover margin (although this is contingent on offense as much as defense), total defense national rank, scoring defense national rank, interceptions caught, and sacks.
|Year||TOV Forced (Rank)||TOV Margin (Rank)||Total Def Rank||Scoring Def Rank||INTs (Rank)||Sacks|
|2000||24 (45)||+0.36 (39)||66||78||10 (76)||32|
|2001||23 (47)||+0.91 (13)||47||25||7 (99)||28|
|2002||31 (28)||+0.50 (35)||14||10||16 (36)||48|
|2003||21 (84)||+0.15 (53)||89||81||11 (79)||??|
|2004||15 (105)||-1.55 (114)||1||25||9 (85)||33|
Turnovers, Total Defense and Scoring Defense
I don't see any relationship between aggregate turnovers forced and total defense. NC State forced one fewer turnover in 2001 than it did in 2000, yet the defense improved from 66th to 47th in total defense. The rankings of each defense in the turnovers forced category don't match up really well with their corresponding rankings in total defense.
Could you say, generally, that a team that's mediocre at forcing TOVs will be mediocre by total defense standards, that a team which forces an above average number of turnovers will be above average in terms of total defense, and so on? That would definitely require a look at the rest of D-IA...
I also threw scoring defense into the table, because I thought, hey, maybe Amato's defenses allow more points when they force fewer turnovers. If that is true, there isn't much of a relationship there, either. Granted, the Amato defense that forced the most turnovers had the highest ranked scoring defense as well; but you'd think that since the defense forced a similar number of turnovers in 2000 and 2001, scoring defense would also be similar between those two seasons. And then there's the matter of the 2005 defense, which matched the 2001 defense's scoring defense rank despite generating eight fewer takeaways (and ranking considerably lower nationally).
What about sacks and INTs?
As far as Chuck Amato's defenses go, there is no indication of an inverse relationship between sacks and interceptions. NC State had 28 sacks in 2001 and just 7 interceptions--both figures are lower than NC State's 2004 totals, which are used as an example in the article for how sacks aversely affect INT totals.
Furthermore, in 2002, NC State had 48 sacks and 16 interceptions. Although the Wolfpack played 14 games that season, both their Sack/Game and INT/Game ratios are still considerably higher than in 2004 (or any other year in the Amato era, for that matter). A whole lot of sacks, a whole lot of INTs.
Man vs. Zone
The other point from the article--that zone defense is more conducive to generating interceptions than man-to-man--may have some merit. Except for 2002, NC State has been in the bottom half of D-IA in passes intercepted. That could be personnel, but it could very well be scheme. I should add that I wish NC State would play more zone; not because of any perceived positive relationship with interceptions, but because I think playing a lot of man-to-man exposes you to big plays more often than is necessary.
Take the Miami game last season, for instance. The Hurricanes used their superior talent and speed to completely torch NC State's man-to-man for over 40+ points. Did the Wolfpack adjust its scheme when the game began to get out of hand? No. And Brock Berlin kept on heaving it over the top.
I fully understand the limitations of looking at one team's statistics over a mere five year period. It isn't my intent to deduce anything about college football defenses in general, but rather to examine the personality and trends of NC State's defense under Chuck Amato.
So are the lack of takeaways in 2004 a concern for NCSU in 2005? Not really, no. NC State has managed to generate at least 20 turnovers in each of Chuck Amato's other seasons, and since there is no doubting that 2004's defense was by far Amato's most talented group, we can hardly cite ineptitude as a reason for the low number of takeaways.
Does a lack of turnovers forced indicate a bad defense? Just in doing a quick scan of turnovers forced by other teams in 2004, I don't think there is any correlation. Several schools with good defenses struggled to force turnovers: Purdue (15 forced), Georgia (17), Virginia (16), Maryland (16), Ohio State (19), Wisconsin (20). And there are plenty of poor defenses that collected a lot of turnovers: Wyoming (29), Rutgers (28), Arizona (27), Nevada (27), Louisiana Tech (27).
What I'm sayin' is... Don't sweat the turnovers. They will come (but even if they don't, that doesn't mean we're doomed to a bad defense).