Defensive Smackdown

The statistic Rex Ryan and many Jets fans like to look to in measuring the effectiveness of Jets defenses during Ryan's tenure is total yards allowed.  Under that metric the Ryan defenses have been very good, though declining every year of Ryan's reign.  In 2009 the Jets defense was indisputably the best defense in the NFL.  It was #1 in yards allowed, #1 in points allowed, #1 against the pass.  That was a truly dominant defense.  In every year since, however, the defense has regressed in terms of total yards allowed.  From #1 in 2009, the defense has trended ever lower, to #3 in 2010, #5 in 2011, #8 in 2012 and finally #11 in 2013.   That is not the best of all possible trend lines, but it still reflects a pretty good defense even at its worst.

However, there is more to defense than just not allowing yards.  After all, the team that allows the fewer yards is not declared the winner after 60 minutes of play.   It's points that count, right?  In this metric Ryan's defenses have not fared nearly as well.  From #1 in 2009 the Jets defense rapidly diminished, to #6 in 2010, #20 in 2011, #20 in 2012, and #19 in 2013.  Ugh.  That progression is downright ugly.  But is it a better, more accurate reflection of the Jets' defensive prowess?  I would argue it is not, for one simple reason: turnovers.  Specifically, the Jets have turned the football over at an alarming rate in every year other than 2010 of the Rex era.  Teams with offenses that constantly hand the ball to the defense are obviously going to give up more points than teams that rarely turn the ball over, all other things being equal.  So even though at a very basic level one could argue that all that matters is points allowed, if you really want to get at which teams have the best defenses it would seem necessary to account for how often the offense turns the ball over.

This conundrum might sway you to revert back to yards allowed as the best measure of a defense, since yards allowed is in theory solely affected by defensive prowess, without being distorted by the effects of offensive turnovers. But is there a better way?  After all, it is certainly possible to envision a defense that gives up chunks of yardage between the 20s while doing two things well: creating turnovers and keeping the opposing team out of the end zone.  This in fact is pretty much what a typical Tampa 2 defense is designed to do.  If effective, such a defense could conceivably be the best defense in football without necessarily ranking all that high in terms of yards allowed.  So, how do we get a better measure of defensive prowess, one that not only takes into account the most important factor of all, points allowed, but also accounts for differing levels of difficulty based on how often the offense turns the ball over, thus increasing the odds of the defense giving up points for reasons that are all about the ineptitude of the offense, not the effectiveness of the defense?

Such a metric would have to solve this important puzzle: how many points is a turnover worth?  If we can quantify how much damage an offensive turnover does to defensive points allowed, then we can devise an "adjusted points allowed" metric which would in theory roughly project how many points every defense "should have" allowed, had every offense committed zero turnovers.  By placing every defense on a level playing field in this theoretical zero offensive turnover universe, we can in theory rank each team's true effectiveness in preventing opposing teams from scoring.  This system would have the virtue of largely eliminating the unfortunate distortions caused by offensive turnovers of ranking defenses by the simpler points allowed method.  It would also have the virtue of eliminating the distortions caused by ranking defenses with wildly divergent defensive philosophies by yards, where a system that is designed to give up yards but not points is unfairly penalized in comparison to a defense that may give up few yards but is inefficient at preventing points.  Finally this new metric would indirectly account for the increased defensive prowess of defenses that generate bunches of turnovers, in that the adjusted points allowed metric is a scoring metric, not a yards metric.  As such this metric will reward defenses that may give up a few more yards but are in fact more effective because they generate lots of turnovers and thereby prevent the opposition from  scoring.

This brings us to the all important question for the purposes of this new metric: how many points is a turnover worth?  If we can't answer this question with a reasonable degree of accuracy then the whole exercise is doomed.  Fortunately for us, there have been several studies that have done fairly sophisticated statistical analysis of this question, and have come up with a fairly consistent answer.  It turns out a turnover is worth just about 4 points.  Some studies place that number slightly higher, some slightly lower, but all come up with close to that same 4 point answer.  How very fortunate for us the math nerds have answered this all important question.  If you're interested in the details of how the mathematicians have answered this question, I refer you to the excellent articles found at Football Outsiders,  SportsRatings, and Sportsquant which detail some of the analysis that went into this answer.  Armed with this information we can proceed to build a metric which should be better than either points allowed or yards allowed in measuring the effectiveness of NFL defenses.

Here's how we build our model.  First we rank all NFL teams by points allowed, since the bottom line in the NFL is points.  Then, for every time each NFL team's offense turned the ball over, we subtract 4 points from the defense's points allowed total.  This simple calculation will in theory remove distortions caused by the offensive turnovers of each team and project just the points the defense should be held accountable for if all offenses had been turnover free.  In effect it levels the playing field for the defenses, and we are left with what should be something approximating a "pure" measure of defensive prowess, free from the distortions of offensive turnovers.  Since I have never seen this metric used anywhere before, unless somebody can point me to a prior author, I get to name this metric.  Yay!  Let's call this metric the Defensive Smackdown ratings.  These ratings should be better than either yards allowed or points allowed in measuring the effectiveness of NFL defenses.  So, without further verbosity, I present the Defensive Smackdown ratings for all NFL defenses during the Rex era.

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2013
Team	Points Allowed	Offensive Turnovers	Virtual Turnover Points	Adjusted Points Allowed	Rank
SEA	231	19	76	155	1
CAR	241	19	76	165	2
CIN	305	30	120	185	3
ARI	324	31	124	200	4
NYG	383	44	176	207	5
SF	273	16	64	209	6
NO	304	19	76	228	7
MIA	335	26	104	231	8
KC	305	18	72	233	9
BAL	352	29	116	236	10
DET	376	34	136	240	11
NE	338	20	80	258	12
SD	348	21	84	264	13
NYJ	387	29	116	271	14
PIT	370	24	96	274	15
BUF	388	27	108	280	16
IND	336	14	56	280	16
STL	364	21	84	280	16
TEN	381	25	100	281	19
CLE	406	29	116	290	20
DEN	399	26	104	295	21
HOU	428	31	124	304	22
TB	389	21	84	305	23
PHI	382	19	76	306	24
WAS	388	14	56	326	25
GB	428	25	100	328	26
ATL	443	28	112	331	27
OAK	453	31	124	331	27
JAX	449	27	108	341	29
DAL	432	20	80	352	30
MIN	480	32	128	352	30
CHI	478	23	92	386	32

Jets

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2012
Team	Points Allowed	Offensive Turnovers	Virtual Turnover Points	Adjusted Points Allowed	Rank
SEA	245	18	72	173	1
CHI	277	24	96	181	2
DEN	289	25	100	189	3
PIT	314	30	120	194	4
SF	273	16	64	209	5
MIA	317	26	104	213	6
CIN	320	26	104	216	7
ARI	357	34	136	221	8
ATL	299	18	72	227	9
NYJ	375	37	148	227	9
SD	350	26	104	246	11
MIN	348	23	92	256	12
NYG	344	21	84	260	13
HOU	331	17	68	263	14
CLE	368	26	104	264	15
STL	348	22	84	264	15
NE	331	16	64	267	17
GB	336	16	64	272	18
CAR	363	22	88	275	19
KC	425	37	148	277	20
IND	387	27	108	279	21
BAL	344	16	64	280	22
DAL	400	29	116	284	23
BUF	435	34	136	299	24
TB	394	23	92	302	25
DET	437	33	132	305	26
PHI	382	19	76	306	27
WAS	388	14	56	332	28
OAK	443	26	104	339	29
JAX	444	26	104	340	30
NO	454	24	96	358	31
TEN	471	28	112	359	32

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2011
Team	Points Allowed	Offensive Turnovers	Virtual Turnover Points	Adjusted Points Allowed	Rank
PIT	227	28	112	115	1
PHI	328	38	152	176	2
SF	229	10	40	189	3
HOU	278	20	80	198	4
MIA	313	25	100	213	5
ARI	348	32	128	220	6
SEA	315	23	92	223	7
CHI	341	29	116	225	8
KC	338	28	112	226	9
NYJ	363	34	136	227	10
WAS	367	35	140	227	10
TEN	317	22	88	229	12
CLE	307	19	76	231	13
CIN	323	22	88	235	14
JAX	329	23	92	237	15
DAL	347	21	84	263	16
NO	339	19	76	263	16
ATL	350	21	84	266	18
DEN	390	30	120	270	19
NE	342	17	68	274	20
BAL	378	24	96	282	21
SD	406	28	112	294	22
DET	387	23	92	295	23
GB	359	14	56	303	24
NYG	400	24	96	304	25
OAK	433	30	120	313	26
BUF	434	30	120	314	27
IND	430	29	116	314	27
STL	407	23	92	315	29
TB	494	40	160	334	30
CAR	429	23	92	337	31
MIN	449	26	104	345	32

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2010
Team	Points Allowed	Offensive Turnovers	Virtual Turnover Points	Adjusted Points Allowed	Rank
GB	240	22	88	152	1
PIT	232	18	72	160	2
CHI	286	31	124	162	3
NYG	347	42	168	179	4
NO	307	31	124	183	5
BAL	270	20	80	190	6
MIN	348	37	148	200	7
SD	322	29	116	206	8
MIA	333	31	124	209	9
CLE	332	29	116	216	10
NYJ	304	21	84	220	11
ATL	288	17	68	220	11
TEN	339	29	116	223	13
TB	318	19	76	242	14
STL	328	21	84	244	15
WAS	377	31	124	253	16
SF	346	23	92	254	17
CIN	395	34	136	259	18
CAR	408	37	148	260	19
OAK	371	26	104	267	20
DET	369	25	100	269	21
BUF	425	39	156	269	21
KC	326	14	56	270	23
NE	313	10	40	273	24
PHI	377	25	100	277	25
SEA	407	31	124	283	26
JAX	419	33	132	287	27
IND	388	25	100	288	28
ARI	434	35	140	294	29
DAL	436	30	120	316	30
HOU	427	18	72	355	31
DEN	471	27	108	363	32

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2009
Team	Points Allowed	Offensive Turnovers	Virtual Turnover Points	Adjusted Points Allowed	Rank
NYJ	236	30	120	116	1
BAL	261	22	88	173	2
DAL	250	19	76	174	3
ARI	325	36	144	181	4
CAR	308	31	124	184	5
SF	281	24	96	185	6
CIN	291	25	100	191	7
NE	285	22	88	197	8
BUF	326	30	120	206	9
IND	307	24	96	211	10
HOU	333	28	112	221	11
PIT	324	25	100	224	12
WAS	336	28	112	224	12
ATL	325	25	100	225	14
NO	341	28	112	229	15
CHI	375	36	144	231	16
GB	297	16	64	233	17
DEN	326	23	92	234	18
MIN	312	18	72	240	19
PHI	337	23	92	245	20
OAK	379	33	132	247	21
CLE	375	31	124	251	22
SD	320	17	68	252	23
TB	400	34	136	264	24
SEA	390	31	124	266	25
MIA	390	29	116	274	26
TEN	402	31	124	278	27
JAX	380	23	92	288	28
NYG	427	31	124	303	29
STL	436	33	132	304	30
KC	424	27	108	316	31
DET	494	41	164	330	32

There are a few things of note here.  First, it is interesting that according to the Defensive Smackdown ratings, the Jets defense has been good but not really elite in any year since 2009.  In fact the Jets defense, despite a near complete overhaul in personnel, has been surprisingly consistent in its ranking.  From 2010 through 2013 the Jets defense ranked #11, #10, #9 and #14.  For Rex detractors these numbers can be used to perhaps show how after the Jets overload blitzes took the league by storm in 2009, the league quickly caught up and the vaunted Rex defense has been just a little better than average ever since.  On the other hand Rex supporters also can draw something from these numbers, as the Jets defense is the only defense in the entire NFL to never rank in the bottom half of the league over the last five years.

Interestingly the Jets defense in 2013, despite being repeatedly burned deep, would likely have come in at just about the same level as the prior three years if it had only been able to generate turnovers at closer to a league average rate.  As it was the Jets were the second worst team in generating turnovers, and although these charts do not capture the net effect of that deficit, it is not difficult to see how the Jets lack of defensive turnovers would have led to more points for opposing offenses.

It may also be interesting to note that since 2009 the Jets defense has not even been the best in the AFC East, ceding that title to the Miami Dolphins every year since, and in 2013 even the lowly Patriots had a better defense than the Jets.  A big part of that picture is the Jets inability to generate a consistent pass rush since 2009 and a decreasing ability to generate turnovers, particularly since Revis left town.  GGN's own Xes&Os wrote a series of insightful fanposts regarding the Jets defense, the pass rush, and turnovers last year which may provide significant insight into these issues. You can check these out here:  Wrong Kind of Defense?, Rex's Pass Rush,  No Turnovers, Ryan Blitzes.

How about you?  Do you think the Defensive Smackdown ratings present an accurate picture of the Jets defense over the years?  What do you see in the numbers and on the field?  Is there something the Jets should be doing differently?  Do you expect to see major improvements in any areas in 2014 and beyond?  Will the Jets ever return to defensive dominance?   Let us know your thoughts in the comments.