A very timely article here:
Green Bay's 7th ranked defense a statistical mirage
By Rick Cina - PackerChatters Staff Tuesday, 17 January 2006
It’s easy to glance at the 7th ranked Green Bay Packers defense and assume that the team must have performed quite well defensively this season.
After all, measuring a defense by how many total yards it allowed has been the most common, most popular means of NFL comparisons for decades. But just because it’s popular to measure a defense that way doesn’t mean it’s not also quite limiting, even misleading.
If we look more closely, we probably find that the 2005 Packer defense may not only have not been very good, it may not even have been good at all.
In many ways, it was an average to below average defense when considering more than just the superficial indicators.
The 1999 defense coordinated by Emmitt Thomas, with an arguably inferior group of players to this past year’s, was by several statistical indicators probably better than the healthier 2005 defense coordinated by Jim Bates.
(For example, the ’99 team amassed 41 turnovers, compiled an impressive 70.0 defensive passer rating, and gave up fewer yards per rush attempt and fewer points per game than the 2005 defense). And all 4 of the defenses coordinated by Ed Donatell were probably better than this year’s defense too. In recent times, only the 2004 defense coordinated by Bob Slowik was worse. And even that defense may not have been dramatically worse than the
2005 defense.
The best pass defense in the league?
Back in 1983, the 5-11 Philadelphia Eagles had the best pass defense in the league. Or at least that’s what their total passing yards allowed statistic said, as no team had allowed fewer passing yards. Yes, the Eagles ranked 25th in the league that year in defensive passer rating (their allowed completion percentage, yards per attempt average, touchdown percentage, and interception percentage). But no matter. They were still the best. Right?
Well, no. There’s a reason why the Eagles were number one in passing yards allowed that season. For one, they were a bad team. And bad teams usually have to play much of the season from behind. When a team plays from behind a lot, their opponents rarely find the need to throw the ball all that often. And, in the Eagles’ case, they didn’t. The Eagles only had to defend 430 passes in 1983. Only one team, the 2-14 Houston Oilers, defended fewer (424), and the Oilers ranked 2nd in pass defense (allowing 47 more passing yards). It’s difficult to give up a lot of passing yards when your opponents rarely throw the ball.
Likewise, the primary reason why the Packers ranked 1st in pass defense at
167.5 pass yards per game (and also one of the main reasons they finished 7th in total defense) is that they too had to defend only 430 passes all season, second only to New Orleans’ 418 (the Saints finished 3rd in passing yards allowed). Put into an historical perspective, no other teams have defended fewer passes than the Saints and Packers did in the previous 6 seasons. In 2004, the 4-12 Dophins (led by Jim Bates) came close, defending only 434 passes (which is also the main reason why Miami finished 8th overall in total defense in 2004, despite finishing 20th in points allowed and 31st against the run). From 1999 to 2004, the total of fewest pass attempts against one team’s defense was, in order, 463, 458, 452, 454, 445, and 434. Those particular 6 teams that defended the fewest pass attempts each year since 1999 averaged just 5 wins per season.
The average pass attempts per season that an NFL team has had to defend since 1999 is 525.9, so the Packers faced almost one hundred fewer pass attempts in 2005 compared to the league average in recent years. When a defense has to defend that many fewer passes, it’s understandable why they give up so many fewer passing yards.
Defending primarily weak passers
Another important reason why the Packers finished 1st in pass defense, and 7th overall, is that they faced just 4 quarterbacks who finished the season with passer ratings above 80.0: Jake Delhomme, Carson Palmer, Brad Johnson, and Matt Hasselbeck. Johnson functioned as a backup this past season, and Hasselbeck threw just 8 passes against the Packers’ defense. Those 4 quarterbacks threw just 96 total passes, or 22.3% of the total passes defended by the Packers. All together, those four 80-plus passer rating quarterbacks were 63 for 96 for 715 yards with 5 touchdowns and 2 interceptions, a 96.5 passer rating. Against the rest of the NFL, those 4 quarterbacks combined for a 94.8 passer rating. In 2004, by comparison, the Packers faced 9 quarterbacks with 80-plus passer ratings, and they had to defend 314 of their 518 total passes from those better performing quarterbacks, 218 more than the 2005 Packers did.
The 2005 Packers faced 14 quarterbacks who finished the season with passer ratings of 79.9 and lower: Harrington, Dilfer, Griese, Bouman, Brooks, Culpepper, Batch, Vick, McMahon, Orton, Garcia, Boller, Grossman, and Wallace. Those 14 quarterbacks combined for 334 pass attempts, which means that 77.7% of the 430 passes the Packers had to defend were thrown by quarterbacks with season-ending passer ratings below 80. All together, those 14 quarterbacks combined for 189 completions in 334 attempts for 2,161 yards with 17 touchdowns and 8 interceptions, an 83.2 passer rating. Against the rest of the NFL, those 14 quarterbacks combined for a pathetic 67.4 passer rating (1,583/2,800 for 17,338 yards, 80 touchdowns, 115 interceptions), a huge differential.
Put together, the Packers faced 18 quarterbacks with a combined 77.3 passer rating against the rest of the NFL, or when not including the passing statistics they compiled against the Green Bay defense. In 2004, the composite passer rating of Packer opponents when playing the rest of the NFL was 88.8.
The final passer rating statistics for all 18 quarterbacks against the Packers was 86.2, which was the second worst for Green Bay in last 47 years (it was an outrageous 99.1 in 2004, and 86.1 in 1958). The Packers allowed
252 completions in 430 attempts (58.6%) for 2,876 yards (6.7 yards per
attempt) with 22 touchdowns and 10 interceptions. The 86.2 passer rating ranked 25th in the league (just like the ’83 Eagles), tied with New Orleans. The Packers ranked 30th in touchdown passes per attempt, 27th in interceptions per attempt, 14th in completions per attempt, and 14th in net passing yards per attempt (subtracting sack yards and dividing by attempts).
So it’s probably fair to say that the Packers really had anything but the best pass defense in the NFL. They were just one the most untested/unchallenged ones.
Other defensive statistics to consider
The Packers started the year out well defending the run, but the run defense got worse as the season went along. In the first 7 games, they had allowed 706 yards in 207 attempts, a 3.4 yards per carry average, and a 100.9 yards per game average. In the last 9 games, the defense allowed 1,310 yards in 296 carries, a 4.4 yards per carry average, and 145.6 yards per game. The Packers finished the year ranked 23rd in run defense (125.6 rushing yards per game), and 18th in rushing yards per attempt (4.0). It should be pointed out, though, that only 5 teams had to defend more than the 504 rushing attempts that the Packers’ defense did, which is the reverse effect of what happened with the pass defense (only one team defended fewer passes), and one of the main reasons why the Packers finished lower in the rankings in total rushing yards allowed.
The total 344 points allowed is the second most (2004) by a Green Bay defense since 1990. The Packers finished tied with Minnesota for 19th in points allowed, moving up 4 ranking slots from 2004, when they ranked 23rd.
The most improved area for the Packers from 2004 to 2005 was big plays allowed. Although they allowed 16 plays of 20 yards or more in the last 4 games, they had allowed just 30 big plays in the previous 12. So all together the defense allowed just 46 plays of 20 yards or more (36 passes, 10 runs) out of 969 total plays defended. In 2004, the Packers allowed an atrocious 74 big plays (60 passes, 14 runs) out of 967 total plays defended, though some of that has to do with facing better quarterbacks who threw the ball more often.
Squelching the big plays may not have been necessarily due to substantially better tackling, however. In a subjective analysis of missed tackles, the Milwaukee Journal Sentinel has indicated that the Packers missed 112 tackles in 16 games in 2005, or 7.0 per game. In 2004, there were 6.9 missed tackles per game. In 2003, 2002, and 2001, there were 6.1, 6.8, and
6.6 missed tackles per game respectively.
The Packers finished with 43 defensive penalties, which was 8 fewer than in
2004 (51), but still more than every other year in the Bob Harlan era. The Packers averaged 34.5 defensive penalties per season from 1990 to 1999, and 29.0 from 2000 to 2003 under Ed Donatell. The defense did improve in this area as the season went along, though, as it had 28 penalties through the first 9 games, and just 15 accepted penalties in the next 7.
The Packers allowed just 35.9% of 3rd downs (74 of 206) to be converted, which ranked a solid 9th in the NFL. That was surprisingly a slightly worse conversion rate than 2004, when the defense allowed 35.0% to be converted (69 for 197).
The Packers were only slightly better in turnovers forced this year compared to last year. They ranked 26th with 21 turnovers forced, compared to tied for last with 15 turnovers forced in 2004. The 21 turnovers included 11 fumble recoveries and 10 interceptions.
The Packers ranked 22nd in the league in red zone defense (53.2%). In Weeks 12-14, the Packers only allowed 1 touchdown in 9 red zone trips. But then in Weeks 15-17, they allowed 8 touchdowns in 9 trips.
To summarize, the Packers tied for 19th in points allowed per game, ranked 18th in rushing yards per attempt, 25th in defensive passer rating (which considers completions, passing yards, passing touchdowns, and interceptions on a per attempt basis), 26th in turnovers per play, 9th in 3rd down conversion rate, and 22nd in red zone defense (touchdowns allowed per red zone appearance.
Toward a better way to rate a defense
There has to be superior ways to measure the effectiveness of a defense rather than just by counting the number of yards allowed, as there are so many other factors to consider other than that one, single statistic.
Fortunately, there has been some progress in recent years with finding better ways to measure defensive performances by looking at multiple categories on a per attempt basis.
Troy Aikman (and others) developed a system of statistical measurement for offensive and defensive statistics that uses 7 categories instead of one and 10 years of statistical data to determine what an average (or normed) score would be. Called the Aikman’s Efficiency Ratings (AER), it uses points allowed per game (minus touchdowns from kick/turnover returns), yards per play (divided into rushing and passing yards per play), turnovers forced, red zone efficiency, first downs allowed, and third down conversion average. All those categories produce a score, with 75 being the normed average. In 2005, the Packers’ final defensive score was 72.5, which meant the Green Bay defense ranked 21st in the league overall.
On the FOOTBALLOUTSIDERS.com website, an increasingly respected play-by-play, weighted system that adjusts for strength of opponent to rank defenses, the Packers ranked 22nd against the pass, 22nd against the run, and 22nd overall using their DVOA ranking system. Broken down further using the handy FOOTBALLOUTSIDERS.com pass defense data, the Packers ranked a solid 8th in the NFL against the opposing team’s #1 wide receiver, but 28th against #2 receivers, 26th against “other” receivers, and 30th against tight ends.
An overrated, untested defense
Finally, it should be said that by all reports Jim Bates, the Packers’
defensive coordinator in 2005, did a very good job this season with the Green Bay defense, especially considering the limited talent he had to work with. He seemed to be a very good coach. But the overall performance of the Packers’ defense probably improved from the D- range in 2004 to the D+ or C- range in 2005. An improvement like that probably isn’t enough to claim that Bates sparked anything close to a dramatic turnaround.
This was a very overrated, untested defense that gets praises heaped upon it primarily because it’s usually only compared to the atrocious 2004 defense, and because the one, non-adjusted measure that is continually cited---7th best in total yards allowed---is looked to as the one statistic that overrides all the others.
There probably needs to be more of an effort to broaden our perspectives and comparisons when assessing the overall performance of a defense.