RBBC, Rushing Concentration, and Outliers

by Chase Stuart on June 18, 2017

In 1984, James Wilder had 407 carries for Tampa Bay at a time when the league was only beginning to shift away from running back by committee. In fact, by the end of the ’84 season, three of the highest single-season carry totals in NFL history had taken place that year, with Walter Payton and Eric Dickerson joining Wilder as true workhorses. The ’84 Bucs had the most concentrated rushing attack of any team in an era of increasingly concentrated rushing attacks.

Take a look: in ’84, Wilder had 1,544 rushing yards, which represented 86.94% of all Bucs rushing yards. The square of that is 75.58%; sum the squares of all players who gained rushing yards for Tampa Bay last year, and you get a concentration index of 75.87%.

Player	Rush	Yds	Perc	Sqrd
James Wilder	407	1544	86.94%	75.58%
Steve DeBerg	28	59	3.32%	0.11%
Mel Carver	11	44	2.48%	0.06%
Jack Thompson	5	35	1.97%	0.04%
Adger Armstrong	10	34	1.91%	0.04%
Michael Morton	16	27	1.52%	0.02%
Gerald Carter	1	16	0.9%	0.01%
Scott Dierking	3	14	0.79%	0.01%
George Peoples	1	2	0.11%	0.00%
James Owens	1	1	0.06%	0.00%
Total	483	1776	100%	75.87%

James Wilder was a one man offense

That was a truly remarkable number in the historical context of 1984. It crushed an NFL record set just one year earlier: the ’83 Rams, with a rookie Dickerson, had a rushing concentration index of 65.95%. Only one other team – the ’81 Oilers — had a concentration index of over 60% when the Bucs hit 76% in 1984.

The average team had a rushing concentration index of 35.5%, and the standard deviation among the teams in 1984 was 13.7%. As a result, Tampa Bay’s rushing concentration index was 2.96 standard deviations above average, known as the Z-Score. That was the 2nd most concentrated score from 1946 to 1984, snugly fit in between the 1966 Patriots (2.93) and 1967 Patriots (2.97).

In 1966, the Patriots led the AFL in rushing attempts and featured a two-back offense with Jim Nance (299 carries) and Larry Garron (101 carries). But since Nance averaged 4.9 yards per carry and Garron just 3.2, Nance wound up rushing for about 74% of the Patriots rushing yards that season. In ’67, New England ran less often, but Nance took a larger share of the load. He had 269 carries to Garron’s 46, and had 76% of all Patriots rushing yards in a very RBBC-centric era. From ’66 to ’67, Nance wasn’t just the top RB in the AFL but in all of pro football. Thanks to his heavy workload, he easily outrushed two HOF RBs in the primes of their career during those seasons.

The table below shows each team that had a Z-Score of at least 1.25 in rushing concentration. Here’s how to read it. In 1991, the Cowboys behind Emmitt Smith had 1,726 rushing yards. ^[1]This excludes any player who finished the season with negative rushing yards. The squared result of each player’s percentage — i.e., the concentration index — was 82.3%. The standard deviation among all teams that year was 13.9%, and the league average was just 33.9%, giving the ’91 Cowboys a Z-Score of 3.48. In other words, the ’91 Cowboys’ rushing attack was so concentrated for that season that it was 3.48 standard deviations above average. That’s why it ranks 1st in this metric.

Rk	Year	Tm	Top RB	Rush Yds	Sqrd	StDev	Lg Avg	Z-Score
1	1991	DAL	Emmitt Smith	1726	82.3%	13.9%	33.9%	3.48
2	1994	DET	Barry Sanders	2080	82.2%	13.3%	40.2%	3.15
3	2007	ARI	Edgerrin James	1441	72.4%	10.3%	40.2%	3.12
4	1999	IND	Edgerrin James	1660	87.7%	15.6%	40.1%	3.06
5	1967	BOS	Jim Nance	1609	58.7%	10%	29.2%	2.97
6	1984	TAM	James Wilder	1776	75.9%	13.7%	35.5%	2.96
7	1966	BOS	Jim Nance	1968	57.8%	9.7%	29.3%	2.93
8	1961	CLE	Jim Brown	2190	48.5%	7.3%	27.4%	2.89
9	2002	BUF	Travis Henry	1615	79.6%	12.5%	44%	2.84
10	1983	RAM	Eric Dickerson	2274	65.9%	11.1%	34.5%	2.84
11	1980	HOU	Earl Campbell	2657	55.8%	9.6%	28.7%	2.83
12	1974	DEN	Otis Armstrong	2165	47.3%	7.3%	26.8%	2.81
13	1960	CLE	Jim Brown	1982	47.5%	7.5%	26.5%	2.81
14	1988	DAL	Herschel Walker	1999	60.1%	10.3%	31.5%	2.78
15	1968	PHI	Tom Woodeshick	1411	48.6%	7.7%	27.4%	2.77
16	2000	IND	Edgerrin James	1861	84.7%	14.9%	44%	2.72
17	2011	JAX	Maurice Jones-Drew	1970	67.3%	11.2%	37%	2.70
18	2014	DAL	DeMarco Murray	2355	63.7%	10.9%	34.9%	2.64
19	1977	CHI	Walter Payton	2811	47.1%	7.5%	27.4%	2.63
20	1981	HOU	Earl Campbell	1737	64%	11.7%	33.5%	2.61
21	1951	NYG	Eddie Price	1713	37.8%	6%	22.2%	2.60
22	1975	BUF	O.J. Simpson	2974	45.2%	7.1%	27%	2.57
23	1965	CLE	Jim Brown	2342	47.5%	7.2%	29.2%	2.54
24	1963	CLE	Jim Brown	2671	53.3%	9%	30.4%	2.53
25	1986	RAM	Eric Dickerson	2478	57.8%	10.3%	31.9%	2.52
26	1978	CHI	Walter Payton	2526	46%	7.2%	28%	2.50
27	1993	ATL	Erric Pegram	1597	57.2%	9.1%	34.6%	2.48
28	2014	PIT	Le'Veon Bell	1773	61.3%	10.9%	34.9%	2.42
29	2012	MIN	Adrian Peterson	2635	64.8%	11.4%	37.2%	2.41
30	1996	DET	Barry Sanders	1810	74.1%	14.2%	40.1%	2.39
31	2005	IND	Edgerrin James	1703	78.8%	14.9%	43.3%	2.39
32	1985	TAM	James Wilder	1644	64.7%	11.5%	37.3%	2.38
33	1988	IND	Eric Dickerson	2257	55.7%	10.3%	31.5%	2.35
34	1969	BOS	Jim Nance	1506	45.9%	7.4%	28.5%	2.35
35	2012	TAM	Doug Martin	1837	64%	11.4%	37.2%	2.34
36	2009	STL	Steven Jackson	1786	63.9%	11%	38.2%	2.34
37	2015	OAK	Latavius Murray	1463	54.9%	8.9%	34.2%	2.33
38	2013	DAL	DeMarco Murray	1504	57.8%	9.5%	35.8%	2.31
39	1946	PIT	Bill Dudley	1317	27.5%	4.4%	17.2%	2.31
40	1998	IND	Marshall Faulk	1488	79%	15.8%	42.8%	2.29
41	1947	NYY	Spec Sanders	2935	31.8%	5.8%	18.7%	2.28
42	1989	DET	Barry Sanders	2055	53%	9.2%	32.3%	2.25
43	1991	DET	Barry Sanders	1930	65.1%	13.9%	33.9%	2.24
44	1997	DET	Barry Sanders	2468	70%	13%	41.3%	2.21
45	2004	IND	Edgerrin James	1861	71.1%	13.2%	41.9%	2.21
46	1992	DET	Barry Sanders	1644	68.5%	14.2%	37.3%	2.20
47	1989	IND	Eric Dickerson	1867	52.3%	9.2%	32.3%	2.18
48	1979	HOU	Earl Campbell	2571	47.2%	8.3%	29.2%	2.17
49	1971	CLE	Leroy Kelly	1578	44.9%	8.1%	27.5%	2.16
50	1985	RAI	Marcus Allen	2262	62.2%	11.5%	37.3%	2.16
51	2006	ARI	Edgerrin James	1341	75.1%	13.8%	45.3%	2.15
52	2009	TEN	Chris Johnson	2592	61.8%	11%	38.2%	2.15
53	1963	OAK	Clem Daniels	1618	49.8%	9%	30.4%	2.15
54	1964	CLE	Jim Brown	2171	50.5%	9.5%	30.1%	2.15
55	1995	DET	Barry Sanders	1760	73.3%	14.6%	42.3%	2.13
56	1999	SEA	Ricky Watters	1424	73.1%	15.6%	40.1%	2.12
57	2001	GNB	Ahman Green	1700	67.7%	12.8%	40.6%	2.12
58	1998	ATL	Jamal Anderson	2119	76.3%	15.8%	42.8%	2.12
59	2013	CHI	Matt Forte	1828	55.7%	9.5%	35.8%	2.09
60	1950	PIT	Joe Geri	1659	27.4%	3.4%	20.2%	2.09
61	2010	TEN	Chris Johnson	1735	64.2%	12.2%	39.2%	2.06
62	1949	CHH	Bob Hoernschemeyer	1080	31.8%	5.8%	20%	2.05
63	1976	CHI	Walter Payton	2387	41.7%	7.1%	27.1%	2.05
64	2016	CHI	Jordan Howard	1737	59.1%	11.2%	36.2%	2.04
65	1973	BUF	O.J. Simpson	3102	46.2%	8.3%	29.5%	2.02
66	1993	RAM	Jerome Bettis	2014	52.9%	9.1%	34.6%	2.01
67	1959	CLE	Jim Brown	2149	50.2%	10.2%	29.6%	2.01
68	1997	OAK	Napoleon Kaufman	1588	67.3%	13%	41.3%	2.00
69	2010	HOU	Arian Foster	2069	63.5%	12.2%	39.2%	2.00
70	2006	STL	Steven Jackson	1805	72.7%	13.8%	45.3%	1.98
71	1977	MIN	Chuck Foreman	1829	42.2%	7.5%	27.4%	1.97
72	1992	DAL	Emmitt Smith	2137	65.3%	14.2%	37.3%	1.97
73	1986	WAS	George Rogers	1732	51.9%	10.3%	31.9%	1.94
74	1947	PHI	Steve Van Buren	1988	29.9%	5.8%	18.7%	1.94
75	1956	SFO	Hugh McElhenny	1836	35.7%	5.8%	24.5%	1.93
76	1979	CHI	Walter Payton	2492	45.2%	8.3%	29.2%	1.93
77	1973	WAS	Larry Brown	1449	45.4%	8.3%	29.5%	1.92
78	1990	DET	Barry Sanders	1927	50.1%	9.1%	32.7%	1.92
79	1954	SFO	Joe Perry	2509	29.3%	3.8%	22.2%	1.90
80	2005	NYG	Tiki Barber	2212	71.4%	14.9%	43.3%	1.89
81	1969	WAS	Larry Brown	1532	42.5%	7.4%	28.5%	1.89
82	1965	NYJ	Matt Snell	1492	42.8%	7.2%	29.2%	1.88
83	1958	CLE	Jim Brown	2526	42.2%	8.4%	26.5%	1.88
84	2004	SEA	Shaun Alexander	2095	66.5%	13.2%	41.9%	1.86
85	2010	STL	Steven Jackson	1592	61.8%	12.2%	39.2%	1.86
86	1971	WAS	Larry Brown	1759	42.4%	8.1%	27.5%	1.84
87	2008	MIN	Adrian Peterson	2345	59.6%	11%	39.5%	1.84
88	1964	NYJ	Matt Snell	1457	47.5%	9.5%	30.1%	1.83
89	1981	NOR	George Rogers	2297	54.9%	11.7%	33.5%	1.83
90	2006	KAN	Larry Johnson	2146	70.5%	13.8%	45.3%	1.82
91	2000	ATL	Jamal Anderson	1219	71.2%	14.9%	44%	1.82
92	1985	DAL	Tony Dorsett	1750	58.1%	11.5%	37.3%	1.81
93	1970	WAS	Larry Brown	2021	39.6%	7.1%	26.7%	1.80
94	1972	WAS	Larry Brown	2090	42%	6.9%	29.5%	1.80
95	1992	PIT	Barry Foster	2156	62.8%	14.2%	37.3%	1.79
96	1968	CLE	Leroy Kelly	2031	41.1%	7.7%	27.4%	1.79
97	1979	PHI	Wilbert Montgomery	2427	43.9%	8.3%	29.2%	1.78
98	1948	DET	Camp Wilson	1360	28.8%	5.7%	18.7%	1.78
99	2012	TEN	Chris Johnson	1687	57.4%	11.4%	37.2%	1.77
100	1955	BAL	Alan Ameche	1833	33.9%	5.8%	23.8%	1.76
101	1962	HOU	Charley Tolar	1742	43.2%	7.7%	29.7%	1.75
102	1970	NYG	Ron Johnson	1799	39.1%	7.1%	26.7%	1.73
103	1949	GNB	Tony Canadeo	2061	29.9%	5.8%	20%	1.73
104	1975	ATL	Dave Hampton	1794	39.2%	7.1%	27%	1.72
105	2015	ATL	Devonta Freeman	1610	49.5%	8.9%	34.2%	1.72
106	1983	ATL	William Andrews	2229	53.5%	11.1%	34.5%	1.72
107	1954	CHI	Chick Jagade	1151	28.6%	3.8%	22.2%	1.71
108	2014	CHI	Matt Forte	1461	53.5%	10.9%	34.9%	1.70
109	1957	CLE	Jim Brown	1963	29.9%	3.7%	23.7%	1.69
110	2003	NOR	Deuce McAllister	2000	68.3%	14.8%	43.5%	1.68
111	1993	BUF	Thurman Thomas	1951	49.9%	9.1%	34.6%	1.68
112	1976	BUF	O.J. Simpson	2566	39%	7.1%	27.1%	1.67
113	2015	TAM	Doug Martin	2162	49%	8.9%	34.2%	1.67
114	2004	NYG	Tiki Barber	1916	64%	13.2%	41.9%	1.67
115	1948	BDA	Mickey Colmer	1818	28.1%	5.7%	18.7%	1.66
116	1964	HOU	Sid Blanks	1353	45.8%	9.5%	30.1%	1.66
117	1952	RAM	Dan Towler	1845	29.4%	5.7%	19.9%	1.66
118	2016	PIT	Le'Veon Bell	1779	54.8%	11.2%	36.2%	1.65
119	1976	MIN	Chuck Foreman	2013	38.9%	7.1%	27.1%	1.65
120	1982	HOU	Earl Campbell	799	47.6%	8%	34.4%	1.65
121	2005	CLE	Reuben Droughns	1503	67.8%	14.9%	43.3%	1.65
122	1984	ATL	Gerald Riggs	1994	57.8%	13.7%	35.5%	1.63
123	1995	DAL	Emmitt Smith	2202	66%	14.6%	42.3%	1.63
124	2004	CIN	Rudi Johnson	1840	63.5%	13.2%	41.9%	1.63
125	2011	ATL	Michael Turner	1840	55.3%	11.2%	37%	1.63
126	1996	NYJ	Adrian Murrell	1587	63.3%	14.2%	40.1%	1.63
127	1979	STL	Ottis Anderson	2582	42.7%	8.3%	29.2%	1.63
128	1993	DAL	Emmitt Smith	2169	49.3%	9.1%	34.6%	1.62
129	2011	TEN	Chris Johnson	1438	55.1%	11.2%	37%	1.62
130	1980	ATL	William Andrews	2407	44.1%	9.6%	28.7%	1.61
131	1969	BAL	Tom Matte	1493	40.4%	7.4%	28.5%	1.61
132	1968	SFO	Ken Willard	1800	39.8%	7.7%	27.4%	1.61
133	2001	CIN	Corey Dillon	1712	61.1%	12.8%	40.6%	1.60
134	1978	HOU	Earl Campbell	2487	39.5%	7.2%	28%	1.60
135	1952	NYG	Eddie Price	1636	29.1%	5.7%	19.9%	1.60
136	1982	RAI	Marcus Allen	1089	47.2%	8%	34.4%	1.60
137	1997	NWE	Curtis Martin	1485	62.1%	13%	41.3%	1.60
138	2002	NOR	Deuce McAllister	1766	64%	12.5%	44%	1.59
139	2001	KAN	Priest Holmes	2018	61%	12.8%	40.6%	1.59
140	1995	NWE	Curtis Martin	1866	65.4%	14.6%	42.3%	1.59
141	2008	DET	Kevin Smith	1333	56.9%	11%	39.5%	1.59
142	1961	GNB	Jim Taylor	2355	39%	7.3%	27.4%	1.59
143	1980	STL	Ottis Anderson	2186	43.9%	9.6%	28.7%	1.59
144	1996	NWE	Curtis Martin	1471	62.7%	14.2%	40.1%	1.59
145	1953	RAM	Dan Towler	2154	30.4%	5.6%	21.5%	1.58
146	1966	CHI	Gale Sayers	1939	44.7%	9.7%	29.3%	1.58
147	1981	MIN	Ted Brown	1513	52%	11.7%	33.5%	1.58
148	1995	ARI	Garrison Hearst	1363	65.1%	14.6%	42.3%	1.57
149	2003	BUF	Travis Henry	1670	66.7%	14.8%	43.5%	1.57
150	2000	NYJ	Curtis Martin	1474	67.4%	14.9%	44%	1.56
151	1986	NYG	Joe Morris	2245	47.9%	10.3%	31.9%	1.56
152	1989	KAN	Christian Okoye	2235	46.6%	9.2%	32.3%	1.55
153	1990	IND	Eric Dickerson	1282	46.8%	9.1%	32.7%	1.55
154	1986	NOR	Rueben Mayes	2074	47.8%	10.3%	31.9%	1.55
155	2007	SFO	Frank Gore	1493	56.2%	10.3%	40.2%	1.54
156	2009	MIN	Adrian Peterson	1928	55.1%	11%	38.2%	1.54
157	1957	CHI	Rick Casares	1700	29.4%	3.7%	23.7%	1.53
158	1982	PHI	Wilbert Montgomery	830	46.6%	8%	34.4%	1.53
159	2002	SDG	LaDainian Tomlinson	2137	63.1%	12.5%	44%	1.52
160	1984	RAM	Eric Dickerson	2869	56.2%	13.7%	35.5%	1.52
161	1982	CIN	Pete Johnson	971	46.5%	8%	34.4%	1.52
162	1998	DEN	Terrell Davis	2472	66.8%	15.8%	42.8%	1.52
163	1981	ATL	William Andrews	1973	51.2%	11.7%	33.5%	1.51
164	2015	IND	Frank Gore	1439	47.6%	8.9%	34.2%	1.51
165	2008	CHI	Matt Forte	1673	56%	11%	39.5%	1.50
166	1952	SFO	Joe Perry	1916	28.5%	5.7%	19.9%	1.50
167	1978	GNB	Terdell Middleton	2023	38.8%	7.2%	28%	1.49
168	1972	BUF	O.J. Simpson	2132	39.9%	6.9%	29.5%	1.49
169	2003	NYJ	Curtis Martin	1635	65.6%	14.8%	43.5%	1.49
170	1974	GNB	John Brockington	1574	37.7%	7.3%	26.8%	1.49
171	1986	SEA	Curt Warner	2311	47.2%	10.3%	31.9%	1.49
172	2010	CIN	Cedric Benson	1524	57.3%	12.2%	39.2%	1.48
173	2015	MIN	Adrian Peterson	2222	47.3%	8.9%	34.2%	1.48
174	1962	RAM	Dick Bass	1689	41.1%	7.7%	29.7%	1.48
175	2016	ARI	David Johnson	1735	52.7%	11.2%	36.2%	1.47
176	2016	LAR	Todd Gurley	1253	52.4%	11.2%	36.2%	1.44
177	1960	GNB	Jim Taylor	2153	37.2%	7.5%	26.5%	1.44
178	2007	SDG	LaDainian Tomlinson	2046	55%	10.3%	40.2%	1.43
179	1966	RAM	Dick Bass	1742	43.2%	9.7%	29.3%	1.43
180	1953	SFO	Joe Perry	2240	29.4%	5.6%	21.5%	1.41
181	2004	NWE	Corey Dillon	2135	60.6%	13.2%	41.9%	1.41
182	1992	HOU	Lorenzo White	1641	57.3%	14.2%	37.3%	1.41
183	1994	DAL	Emmitt Smith	1958	59%	13.3%	40.2%	1.41
184	1958	PHI	Billy Ray Barnes	1101	38.2%	8.4%	26.5%	1.41
185	1973	GNB	John Brockington	1977	41.1%	8.3%	29.5%	1.40
186	2006	CIN	Rudi Johnson	1641	64.7%	13.8%	45.3%	1.40
187	1995	ATL	Craig Heyward	1394	62.6%	14.6%	42.3%	1.40
188	1975	CLE	Greg Pruitt	1856	36.9%	7.1%	27%	1.39
189	1980	CLE	Mike Pruitt	1681	41.9%	9.6%	28.7%	1.38
190	1996	PHI	Ricky Watters	1886	59.5%	14.2%	40.1%	1.36
191	1974	BUF	O.J. Simpson	2094	36.7%	7.3%	26.8%	1.36
192	1983	SEA	Curt Warner	2119	49.5%	11.1%	34.5%	1.35
193	2010	ATL	Michael Turner	1900	55.5%	12.2%	39.2%	1.34
194	2011	BAL	Ray Rice	1996	51.9%	11.2%	37%	1.33
195	1973	NYG	Ron Johnson	1488	40.5%	8.3%	29.5%	1.33
196	2004	WAS	Clinton Portis	1774	59.5%	13.2%	41.9%	1.33
197	2001	NOR	Ricky Williams	1714	57.4%	12.8%	40.6%	1.31
198	1967	CLE	Leroy Kelly	2160	42.3%	10%	29.2%	1.31
199	2016	MIA	Jay Ajayi	1825	50.9%	11.2%	36.2%	1.30
200	1971	BUF	O.J. Simpson	1337	38%	8.1%	27.5%	1.30
201	2006	NYG	Tiki Barber	2156	63.3%	13.8%	45.3%	1.30
202	1977	CLE	Greg Pruitt	2205	37.2%	7.5%	27.4%	1.30
203	1976	WAS	Mike Thomas	2127	36.3%	7.1%	27.1%	1.29
204	1962	GNB	Jim Taylor	2464	39.6%	7.7%	29.7%	1.29
205	1971	GNB	John Brockington	2235	37.9%	8.1%	27.5%	1.29
206	1997	GNB	Dorsey Levens	1916	58%	13%	41.3%	1.29
207	1972	GNB	John Brockington	2138	38.4%	6.9%	29.5%	1.28
208	1959	SFO	J.D. Smith	1839	42.8%	10.2%	29.6%	1.28
209	1972	NYG	Ron Johnson	2022	38.3%	6.9%	29.5%	1.28
210	2011	STL	Steven Jackson	1681	51.2%	11.2%	37%	1.27
211	1955	PIT	Fran Rogel	1285	31.1%	5.8%	23.8%	1.27
212	2001	WAS	Stephen Davis	1955	56.8%	12.8%	40.6%	1.27
213	1990	KAN	Barry Word	1954	44.1%	9.1%	32.7%	1.26
214	1990	DEN	Bobby Humphrey	1872	44.1%	9.1%	32.7%	1.25
215	2003	NYG	Tiki Barber	1568	61.9%	14.8%	43.5%	1.25

It’s impossible to write about rushing concentration and not discuss Edgerrin James. He has six seasons in the top 61, but perhaps more impressively, his teams have 5 of the top 15 most highly concentrated rushing offenses in league history. That’s remarkable. Ditto goes for Jim Brown, whose teams basically finished 1st in 8 of his 9 seasons playing pro football.

References[+]

References
↑1	This excludes any player who finished the season with negative rushing yards.

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