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Defending Reality

Nearly every Fantasy League has different rules for how to score Team Defense. Many used the tried and true method of 1 point for a sack and 2 for a turnover. To add a little variety, many also add 6 points for the rare touchdown and yet another two for the rarest score, a safety. Other leagues try to tweak this scoring method by incorporating points against, yards against, or both.

Fantasy Football Scoring - A History Lesson

The basis for fantasy scoring comes from an attempt to quantify an individual player's performance numerically and assign that a value proportional to his team's performance. Touchdowns and yardage usually translate to team success, and the offensive player is rewarded for such productivity.

The second iteration of fantasy scoring came about as an attempt to normalize different positions to a similar scoring system. Quarterbacks produce more touchdowns and yardage than running backs, who produce even more than wide receivers. The result for many leagues was to reduce the points for passing touchdowns and also passing yardage so as to make running backs more valuable. Other leagues go one step further by awarding an extra point per catch to each player to increase wide receiver and tight end values closer to running backs.

What does any of this have to do with Team Defense? I am glad that you asked that question. This article is an attempt to determine how to quantify Team Defense scoring in a manner that reflects the impact a defense has on the outcome of a game, and also to provide a normalized score for a Team Defense that puts the value of a Defense at or near par for other fantasy football positions.

Baseline Defense

First, we have to determine what constitutes a good Team Defense. Is it one that gives up the fewest yards, or the fewest points? An argument can be made for either being the case, so let's take a look at the rankings from last year to see which method more accurately reflects a successful season. The results for the 2004 Season are in Table 1:

Table 1: Baseline Defense Rankings

Team
YPG Rk
PtsVs Rk
Avg Rk
Pittsburgh
1
1
1
Washington
3
5
4
Buffalo
2
8
5
NY Jets
7
4
5.5
New England
9
2.5
5.75
Baltimore
6
6
6
Philadelphia
10
2.5
6.25
Denver
4
9.5
6.75
Tampa Bay
5
9.5
7.25
Jacksonville
11
7
9
Arizona
12
12
12
Miami
8
20
14
Atlanta
14
14
14
San Diego
18
11
14.5
NY Giants
13
17
15
Chicago
21
13
17
Carolina
20
15.5
17.75
Houston
23
15.5
19.25
Cleveland
15
24
19.5
Cincinnati
19
21
20
Detroit
22
18
20
St. Louis
17
25
21
Dallas
16
27.5
21.75
Green Bay
25
23
24
Seattle
26
22
24
Indianapolis
29
19
24
Minnesota
28
26
27
San Francisco
24
32
28
Tennessee
27
30.5
28.75
New Orleans
32
27.5
29.75
Kansas City
31
29
30
Oakland
30
30.5
30.25

Upon further review of Table 1, the Top 3 teams in Points Against were three of the four teams in the conference championship games. In fact, all 8 division winners and 10 of 12 playoff teams ranked equally or better in Points Against than in Yardage Against. We shall adopt Points Against as the baseline for Team Defense.

Sack the Sack

The most common scoring system for Team Defense awards a point for every sack. This seems like a good idea, since it is an accomplishment by the defense to stop the offense from moving downfield, and it is an easy statistic to track. However, how realistic is this as a measure of Team Defense? Do sacks truly translate to team victories?

We obviously need some way to test this idea. Turning to statistics, we find that correlation is a measure of how two groups of statistics relate to one another. The formula used for correlation gives an answer between 0 and 1, with 1 representing a perfect match - 100% correlation. We can use this to see if sacks line up with our baseline, the Baseline Ranking (Points Against) from Table 1.

Table 2 lists the Team Defense rankings for sacks and the Baseline Ranking from Table 1. The correlation factor is given at the bottom of the table.

Table 2: Sacks vs. Baseline Defense Rankings

Team
Sacks
Rank
PtsVs Rk
Pittsburgh
41
7
1
Washington
40
9
5
Buffalo
45
3
8
NY Jets
37
17
4
New England
45
3
2.5
Baltimore
39
12
6
Philadelphia
47
2
2.5
Denver
38
14
9.5
Tampa Bay
45
3
9.5
Jacksonville
37
17
7
Arizona
38
14
12
Miami
36
21
20
Atlanta
48
1
14
San Diego
29
28
11
NY Giants
40
9
17
Chicago
35
23
13
Carolina
34
24
15.5
Houston
24
32
15.5
Cleveland
29
28
24
Cincinnati
37
17
21
Detroit
38
14
18
St. Louis
34
24
25
Dallas
33
26
27.5
Green Bay
40
9
23
Seattle
36
21
22
Indianapolis
45
3
19
Minnesota
39
12
26
San Francisco
29
28
32
Tennessee
32
27
30.5
New Orleans
37
17
27.5
Kansas City
41
7
29
Oakland
25
31
30.5
Correlation
0.509

Based upon the results, it would appear that there is weak correlation (50.9%) between Sacks and Baseline Defensive Ranking. Why would that be the case?

The common misconception is that a sack translates readily to the defense getting the ball back for the offense. The reality is that not all sacks are created equal. While a 15-yard sack on 3rd-and-10 would likely result in a Team Defense getting the ball for the offense, a 1-yard sack on first down is not nearly as valuable. However, in the 1 point for a sack scoring system, there is no differentiation between the two different sacks. It would appear that the sack statistic is misleading, and should be replaced by another one.

Turning Over Turnovers

Perhaps we should look harder at the other common statistic used in Team Defense scoring, the turnover. Surely one cannot dispute that turnovers relate strongly to team victories. That has to correlate well with Team Defense rankings, right?

Table 3: Turnovers vs. Baseline Defense Rankings

Team
TOs
Rank
PtsVs Rk
Pittsburgh
32
11
1
Washington
26
22
5
Buffalo
39
1
8
NY Jets
33
8
4
New England
36
3
2.5
Baltimore
34
7
6
Philadelphia
28
17
2.5
Denver
20
29
9.5
Tampa Bay
27
21
9.5
Jacksonville
28
17
7
Arizona
30
13
12
Miami
25
23
20
Atlanta
32
11
14
San Diego
33
8
11
NY Giants
28
17
17
Chicago
29
16
13
Carolina
38
2
15.5
Houston
30
13
15.5
Cleveland
28
17
24
Cincinnati
36
3
21
Detroit
24
24
18
St. Louis
15
31
25
Dallas
22
25
27.5
Green Bay
15
31
23
Seattle
35
6
22
Indianapolis
36
3
19
Minnesota
22
25
26
San Francisco
21
27
32
Tennessee
30
13
30.5
New Orleans
33
8
27.5
Kansas City
21
27
29
Oakland
18
30
30.5
Correlation
0.412

Okay, things just took another turn for the worse. How can a correlation lower than sacks be explained?

The answer really comes from the mathematics - correlation does not work well with numbers that are close together. From Table 3, you can see most Team Defenses (25 of 32) have from 20 and 35 turnovers, so such a tight grouping will compromise the calculations.

A sanity check is in order - we need to use the common scoring method in its entirety (1 point per sack + 2 points for a turnover) and correlate that result against Average Points (See Table 4):

Table 4: Turnovers and Sacks vs. Baseline Defense Rankings

Team
TOx2+Sk
Rank
PtsVs Rk
Pittsburgh
105
9
1
Washington
92
19
5
Buffalo
123
1
8
NY Jets
103
10
4
New England
117
2
2.5
Baltimore
107
7
6
Philadelphia
103
10
2.5
Denver
78
27
9.5
Tampa Bay
99
13
9.5
Jacksonville
93
17
7
Arizona
98
14
12
Miami
86
21
20
Atlanta
112
4
14
San Diego
95
16
11
NY Giants
96
15
17
Chicago
93
17
13
Carolina
110
5
15.5
Houston
84
24
15.5
Cleveland
85
23
24
Cincinnati
109
6
21
Detroit
86
21
18
St. Louis
64
31
25
Dallas
77
28
27.5
Green Bay
70
30
23
Seattle
106
8
22
Indianapolis
117
2
19
Minnesota
83
25
26
San Francisco
71
29
32
Tennessee
92
19
30.5
New Orleans
103
10
27.5
Kansas City
83
25
29
Oakland
61
32
30.5
Correlation
0.558

Now we're getting somewhere. The correlation between the basic scoring system and Points Against is 55.8%, slightly stronger than the sack correlation. The combination of both statistics helped in achieving point separation (ranging from 61 to 123 points) and agreement with the baseline, but there is definitely room for improvement.

The basic argument against using the sack as a standard measure remains - there is little direct correlation between the sack and elite defenses. Another measure of defense should be considered in place of sacks. However, if sacks are going to be eliminated from the Team Defense scoring system, what will be inserted in its place?

Give Me The $#@!! Ball

Let us reconsider the basic premise of Team Defense. Defenses have two main objectives - keeping the opposition from scoring, and getting the ball back for their offense. We have already seen that the first objective is the baseline measure of Team Defense, so we need to quantify the second criteria to the best of our ability to see if this should be the new fantasy football measure of a defense.

There are two defensive categories of getting the ball back for the offense that are overlooked in the "turnover" category. Defenses succeed in stopping the opponent by forcing the traditional turnover (fumbles and interceptions) and also by forcing punts and stopping the opponent on fourth down. Our new formula for Team Defense needs to have basis in reality to weigh the value of forced punts and turnovers on downs.

Punts happen numerous times during the game, but they rarely result in the defense giving the offense a short field (under 50 yards from a touchdown). As such, forcing a punt has to be viewed as less opportunistic and less valuable than a fumble or interception, which results in a short field about half of the time. Therefore, our formula begins to look like this:

New Team Defense Score = Turnovers (INTs and Fumbles) x 2 + Forced Punts

Now for the second portion of the new formula - incorporation of turnovers on downs. While this can happen anywhere on the field, it is more likely to occur at both a crucial point in the game and also in a position where the opposing team is in scoring territory. While the resulting field position may not be as good as with a traditional turnover, the impact of both getting the ball for the offense and the likelihood that the 4th down turnover kept the opposition off the scoreboard gives this type of turnover approximately equal value to a fumble or interception. Therefore, we modify the formula to be:

New Team Defense Score = Turnovers (INTs + Fumbles + 4th Down Stops) x 2 + Forced Punts

We label this new equation the "Realistic Team Defense" scoring system. Now all that is left is to test our new formula.

Is the Fantasy a Reality

Let us revisit the 2004 season for data once again. Obtaining the two new statistics (4th down turnovers and forced punts), we get the following results:

Table 5: All Turnovers and Forced Punts vs. Baseline Defense Rankings

Team
TOx2+FPs
Rank
PtsVs Rk
Pittsburgh
155
13
1
Washington
137
25
5
Buffalo
164
7
8
NY Jets
171
4
4
New England
175
1
2.5
Baltimore
174
2
6
Philadelphia
164
7
2.5
Denver
153
15
9.5
Tampa Bay
151
17
9.5
Jacksonville
140
21
7
Arizona
168
6
12
Miami
158
11
20
Atlanta
155
13
14
San Diego
152
16
11
NY Giants
149
20
17
Chicago
172
3
13
Carolina
151
17
15.5
Houston
138
23
15.5
Cleveland
159
10
24
Cincinnati
171
4
21
Detroit
156
12
18
St. Louis
111
32
25
Dallas
132
26
27.5
Green Bay
119
29
23
Seattle
150
19
22
Indianapolis
162
9
19
Minnesota
115
31
26
San Francisco
127
28
32
Tennessee
140
21
30.5
New Orleans
138
23
27.5
Kansas City
128
27
29
Oakland
119
29
30.5
Correlation
0.624

Definite progress. The correlation between the new and improved scoring system and Points Against is finally over 60% (62.4%), a sign of a strong correlation and the best correlation so far. The addition of all turnovers and punts forced has increased the point separation once again (now ranging from 111 to 175), albeit slightly (a range of 64 points instead of 62 as before in Table 4).

There are additional benefits to this new equation. First, the scores are higher (average score of 9.3 / game) than under the original system (5.9 / game), which goes more towards a better normalization of the Team Defense position on the fantasy roster. By increasing the average score, the net effect is that a Team Defense is now representative of another normalized position player. Table 6 represents the 2004 average score by position of the Top 12 players based upon the default Footballguys.com scoring system.

Table 6: Average Fantasy Points / Game for Top 12 Players by Position

Pos
Top 12
QB
19.74
RB
15.53
WR
12.18
TE
6.68
PK
7.58
Def
10.39*

*Based upon the new Realistic Team Defense formula.

Now the Team Defense is comparable to the value of just under a Top 12 wide receiver. That would seem to be an appropriate position of value for a strong Team Defense, below a skill position (QB, RB, WR) but above the lesser valued tight end or kicker position.

One last additional benefit (and variance to the Realistic Team Defense formula) is that the addition of scoring points for a Team Defense scoring play (Touchdown or Safety) allows for the added point value, and also reduces the impact of that event to a lower percentage of the total Team Defense score. Previously, under the original scoring method, teams scored between 61 and 123 points for the season without defensive or special teams touchdowns added (see Table 4). Adding a single touchdown (6 points) varied the overall season score by 5-10%, a large impact. Now with the Realistic Team Defense formula, adding a touchdown reduces the impact to 3-5% (see Table 5). This valuation relative to the seasonal performance does seem to be more appropriate than the twice as large prior method.

Conclusion

Adoption of the Realistic Team Defense formula for defensive scoring for fantasy leagues going forward would result in a more accurate representation of the value of a Team Defense and better reflect how the actual defensive unit for each team performs in that particular season. The formula incorporates the significant statistics to quantify how well an actual defense performs, and results in a normalized score relative to the skill position players. The variation of adding back in the relatively rare event of a defensive score reduces the impact of the additional points to less of an overall change to the season Team Defense total, and increases the relative value of a Team Defense closer to that of an upper echelon wide receiver.

Data Sources:
www.nfl.com
www.espn.com
www.footballguys.com

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