The quality of a defense

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cstelter
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Posts: 818
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The quality of a defense

Post by cstelter »

Hi All,
Having never played football, I really have no 'eye test' to go on, but being an engineer, I do enjoy a dive into numbers.

One thing I determined back in the early 2000's is that one cannot rely on absolute numbers to determine a good defense. One season we got off to a hot start, and our defense looked superb. However, in studying the stats that season, it seemed that we played a lot of bad offensive teams, and we seemed to have an absurd number of TO's. Midseason, we hit a string of outstanding offenses and our turnovers evaporated and so did our supposedly good defense. When comparing the Vikings performance that season against the opposing team offensive average, one found that in nearly every case we *underperformed* against that average on defense. So while on an absolute scale, our numbers were awesome, relative to how the opposing teams normally did-- they did even better against us.

So I've used this metric numerous times since then and it generally bears reasonably accurate for assessing the true quality of a defense.

So how are the Vikings doing this season??

First of all, I love http://www.pro-football-reference.com and their querying tools as it helps a lot in getting at the data you want to see. So all the data here is pretty much from that site. I'll include the link to the query when appropriate.

First of all, let's look at this season's opponents

click here for the actual table on pro-football-reference.com.

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                                Passing                                            Rushing            Tot Yds & TO            
Tm  Year  G  W  L  T   W-L%  Cmp  Att  Cmp%  Yds   TD  Int  Sk  Yds  Rate  NY/A    Att  Yds  Y/A  TD  Tot  Ply  Y/P     DPly  DY/P  TO  ToP
TEN  2016  1  0  1  0  0     25    41  61    252    2    1   2   19  86.5  5.8605   22   64  2.91  0  316   65  4.8615    61  4.9344  3  0:30:25
GNB  2016  1  0  1  0  0     20    36  55.6  180    1    1   5   33  70.7  4.3902   23   83  3.61  1  263   64  4.1094    57  4.9825  3  0:29:42
CAR  2016  1  0  1  0  0     22    36  61.1  201    0    3   8   64    49  4.5682   28  105  3.75  1  306   72  4.25      54  3.9074  3  0:34:52
NYG  2016  1  0  1  0  0     25    45  55.6  261    0    1   0    0  63.3  5.8      18   78  4.33  1  339   63  5.381     69  5.3043  2  0:24:28
HOU  2016  1  0  1  0  0     19    42  45.2  155    1    1   4   29  56.1  3.3696   14   59  4.21  0  214   60  3.5667    69  5.087   1  0:22:32
You have to love that opposing QB rating column, Tot Yds rushing and passing-- all top 3 in the league iirc.

This link points to how opposing teams have fared against us in the Zimmer era

But reading the Eagle Fan Forum points, most folks deprecate these numbers by claiming that we haven't beaten the best of teams.

So I go here to see how these teams have done (unfortunately including the Vikings as excluding just that one game seems beyond the query capabilities of the site). Also I couldn't figure out how to pick just these 5 teams in this order, so I had to do some editing in excel to get this trimmed output

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                                 Passing                                           Rushing             Tot Yds & TO            
Tm   Year  G  W  L  T  W-L%  Cmp  Att  Cmp%  Yds   TD  Int  Sk  Yds  Rate  NY/A    Att  Yds  Y/A  TD   Tot  Ply  Y/P    DPly  DY/P    TO  ToP
TEN  2016  6  3  3  0  0.5   117  189  61.9  1317  10    6   9   55  88.3  6.6515  179  880  4.92  5  2197  377  5.8276  355  5.4761   9  3:11:40
GNB  2016  6  4  2  0  0.667 148  237  62.4  1436  13    4  11   60  91.7  5.7903  151  629  4.17  2  2065  399  5.1754  353  5.3371  10  3:09:36
CAR  2016  6  1  5  0  0.167 140  232  60.3  1640  10   10  15  109  80.2  6.6397  164  726  4.43  7  2366  411  5.7567  380  5.8658  16  3:06:12
NYG  2016  6  3  3  0  0.5   151  233  64.8  1729  8     6  11   59  88.8  7.0861  127  456  3.59  3  2185  371  5.8895  424  5.1462  13  2:36:44
HOU  2016  6  4  2  0  0.667 134  227  59    1299  8     8  12  103  74.1  5.4351  162  667  4.12  1  1966  401  4.9027  371  5.1051  10  3:02:47
So you can see that not only are our Vikings doing well in an absolute sense, nearly across the board, we've allowed significantly fewer yards per play in both passing and rushing yards
Finally, with the above two tables in excel, I wrote a calculation to exclude the Vikings numbers from the total numbers and take the Vikings numbers as a percent of all other opponents.

Code: Select all

                                      Passing                                                          Rushing                       Tot Yds & TO            
Tm   Year  G  W  L  T  W-L%  Cmp      Att   Cmp%     Yds     TD    Int      Sk     Yds  Rate    NY/A    Att    Yds  Y/A       TD     Tot   Ply    Y/P   DPly   DY/P     TO  
TEN  2016  6  3  3  0  0.5  135.9% 138.5%  98.3%  118.3% 125.0% 100.0%  142.9%  263.9%  98.0%  87.9%  70.1%  39.2%   54.7%   0.0%  84.0% 104.2% 81.0% 103.7%  90.1% 250.0%  
GNB  2016  6  4  2  0  0.67 78.1%   89.6%  87.2%   71.7%  41.7% 166.7%  416.7%  611.1%  77.0%  75.5%  89.8%  76.0%   82.9% 500.0%  73.0%  95.5% 76.1%  96.3%  93.3% 214.3%  
CAR  2016  6  1  5  0  0.17 93.2%   91.8%  101.6%  69.8%   0.0% 214.3%  571.4%  711.1%  61.0%  68.4% 102.9%  84.5%   83.2%  83.3%  74.3% 106.2% 70.6%  82.8%  66.6% 115.4%  
NYG  2016  6  3  3  0  0.5  99.2%  119.7%  83.4%   88.9%   0.0% 100.0%    0.0%    0.0%  71.2%  81.6%  82.6% 103.2%  125.8% 250.0%  91.8% 102.3% 90.1%  97.2% 103.1%  90.9%  
HOU  2016  6  4  2  0  0.67 82.6%  113.5%  73.2%   67.7%  71.4%  71.4%  250.0%  195.9%  75.6%  61.6%  47.3%  48.5%  102.5%   0.0%  61.1%  88.0% 68.5% 114.2%  99.6%  55.6%  
This table is just impressive to my eye. Certain things jump out at you. Our sack and yards per sack are just ridiculous. Our opposing QB rating is obviously superb absolutely, but across the board better than normal for the teams we have faced.

TEN passed a whole lot more than usual against us, probably because we shut down their preferred running attack. Still we held them to only 84% of the total yards they normally enjoy.

Seems our Y/A rushing allowed has eroded over the season, but I'm not sure that is a source for worry-- our two most convincing victories have come in these past 2 games, giving up just 23 points while scoring 55. Also, in these last 2 games we've relied far less on TO.

Our TO percent vs opposing average has declined every week. A bit of a puzzler, but winning dominantly with fewer TO's is only a positive in my book. Probably the book on beating MN is don't turn the ball over and try to run as much as possible. Well, it hasn't worked for either NYG or HOU even though it would seem they had some success in these areas. If anything, this seems most concerning in the whole analysis.

All this shows what we already know-- we have a quality defense. But we've had years when this same analysis revealed that it was really more a matter of who we played than how well we played.

I certainly hope we can keep this up!
Craig S
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autobon7
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Joined: Wed Sep 30, 2015 12:20 pm

Re: The quality of a defense

Post by autobon7 »

Wow....that's an impressive amount of useful data you have put together. Very enjoyable read that kind of solidifies what we are all thinking. We have possibly the leagues best defense. One little "thing" I'd like to add is that the Viks are continuing to prove folks wrong and accomplishing things that held them back in years past like failing to win on prime time, failing to win on the road, failing to beat teams with winning records, failing to beat last years playoff teams, etc. This all started last year and having a winning record in a temporary stadium. Now we need to show the league we will not come out flat after a bye.

Skol Vikings......and thanks other Craig for taking the time to put this data together.
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