Adjusting Passer Rating for Era: Completion Percentage Rankings (Thru 2018)

by Chase Stuart on April 6, 2019

Baugh about to complete a pass, probably.

Regular readers know that I have spent some time over the past few years adjusting passer rating for era. One valuable part of the methodology is that we can also adjust each of the four component parts — completion percentage, yards per attempt, touchdown percentage, and interception percentage — for era.

Let’s take completion percentage. The passer rating formula measures completion percentage by taking a passer’s completion percentage, subtracting 30%, and multiplying the result by five. This made sense when the average completion percentage was around 50%; in that case, 50% minus 30% equals 20%, and multiplying that by 5 gives a result of 1.00.

To adjust for era, we replace “30%” in that formula with “league average minus 20%.” So in 2018, the league average completion percentage was 64.9%, which means we would use 44.9% for this formula. Drew Brees completed 74.4% of his passes; if we subtract the baseline from his result, we get 29.5%. Multiply that result by 5, and Brees gets a completion percentage score of 1.48 for 2018.

If we do this for every quarterback in every season of his career, and then weight each season by his number of pass attempts, we can get career grades. This is one way to come up with career completion percentages adjusted for era.

The overwhelming champion in this regard is Sammy Baugh, who led the NFL in completion percentage 8 times during the decade of the ’40s. As recently as 1975, Baugh was still 4th all-time in career completion percentage, and less than 1% off of the leader. Baugh has a rating of 1.58, which means on average he was better at completing passes relative to his era than Brees was in 2018.

The top passers in measuring completion percentage this way are Baugh followed by a who’s who of the completion percentage kings: Len Dawson, Otto Graham, Steve Young, Joe Montana, Sid Luckman, and Drew Brees.

The bottom 5? Rex Grossman, Jay Schroeder, Doug Williams, Mike Pagel, and the man at the very bottom of the list is… Derek Anderson.

The table below shows the 189 passers with 1,500 career pass attempts. Here’s how to read the table below: Baugh has the best adjusted completion percentage, and he threw 2,995 career attempts. He played from 1937 to 1952, and has an era-adjusted passer rating of 92, which ranks 3rd. He has a completion percentage grade of 1.58. The final column? That shows Baugh’s completion percentage grade relative to the other 3 variables in the passer rating formula (Y/A, TD%, and INT%). So Baugh is +0.27 better in completion percentage than the other 3 metrics, on average.

Cmp % Rk	Player	Att	First Yr	Last Year	EA PR	EA PR Rk	Cmp%	Cmp% vs. Other3
1	Sammy Baugh	2995	1937	1952	92	3	1.58	0.27
2	Len Dawson	3741	1957	1975	86.6	4	1.40	0.13
3	Otto Graham	2626	1946	1955	95.2	1	1.40	-0.04
4	Steve Young	4149	1985	1999	86.5	5	1.36	0.09
5	Joe Montana	5391	1979	1994	83.8	7	1.36	0.14
6	Sid Luckman	1744	1939	1950	93.9	2	1.33	-0.11
7	Drew Brees	9783	2001	2018	79.4	17	1.31	0.15
8	Bart Starr	3149	1956	1971	78.7	20	1.30	0.16
9	Ken Stabler	3793	1970	1984	73.3	45	1.30	0.27
10	Chad Pennington	2471	2000	2010	75.4	29	1.30	0.23
11	Kurt Warner	4070	1998	2009	79.8	14	1.29	0.13
12	Ken Anderson	4475	1971	1986	79.8	13	1.28	0.11
13	Y.A. Tittle	4395	1948	1964	77.8	22	1.28	0.15
14	Frankie Albert	1564	1946	1952	81.8	9	1.27	0.06
15	Peyton Manning	9380	1998	2015	81	11	1.27	0.07
16	Sonny Jurgensen	4262	1957	1974	80.3	12	1.27	0.08
17	Fran Tarkenton	6467	1961	1978	79.7	16	1.25	0.08
18	Bob Griese	3429	1967	1980	79	19	1.25	0.09
19	Norm Van Brocklin	2895	1949	1960	81.6	10	1.24	0.03
20	Roger Staubach	2958	1969	1979	84.6	6	1.23	-0.06
21	Troy Aikman	4715	1989	2000	71.1	64	1.21	0.19
22	Tony Romo	4335	2004	2016	79.2	18	1.21	0.03
23	Dan Fouts	5604	1973	1987	75.4	30	1.21	0.11
24	Danny White	2950	1976	1988	74.3	38	1.21	0.12
25	Bob Waterfield	1617	1945	1952	74.6	35	1.20	0.10
26	Daunte Culpepper	3199	1999	2009	74.1	39	1.18	0.09
27	Brian Griese	2796	1998	2008	69.6	86	1.18	0.18
28	John Brodie	4491	1957	1973	70.9	68	1.18	0.15
29	Jim Kelly	4779	1986	1996	74.9	33	1.17	0.07
30	Kirk Cousins	2702	2012	2018	72.2	53	1.17	0.12
31	Matt Ryan	6201	2008	2018	74.6	36	1.17	0.07
32	Johnny Unitas	5186	1956	1973	77.2	23	1.16	0.01
33	Bernie Kosar	3365	1985	1996	73	47	1.16	0.09
34	Brad Johnson	4326	1994	2008	70.4	73	1.16	0.14
35	Billy Wade	2523	1954	1966	70.8	69	1.16	0.13
36	Brett Favre	10169	1991	2010	73.3	44	1.16	0.08
37	Matt Schaub	3281	2004	2018	71.7	58	1.15	0.10
38	Greg Landry	2300	1968	1984	73.6	41	1.15	0.07
39	Dan Marino	8358	1983	1999	76.9	25	1.15	0.00
40	Tom Brady	9375	2000	2018	79.7	15	1.15	-0.06
41	Frank Tripucka	1745	1949	1963	61.3	164	1.15	0.31
42	Aaron Rodgers	5492	2005	2018	82.9	8	1.14	-0.13
43	Philip Rivers	7000	2004	2018	76.1	27	1.14	0.00
44	Ken O'Brien	3602	1984	1993	72	55	1.14	0.08
45	Ben Roethlisberger	7168	2004	2018	75	32	1.14	0.02
46	Milt Plum	2419	1957	1969	70.7	70	1.14	0.10
47	Bert Jones	2551	1973	1982	77.2	24	1.13	-0.04
48	Tony Eason	1564	1983	1990	71.5	60	1.13	0.08
49	Bobby Hebert	3121	1985	1996	69.4	87	1.12	0.11
50	Rich Gannon	4206	1987	2004	73.5	42	1.12	0.02
51	Jeff Garcia	3676	1999	2009	74.3	37	1.12	0.00
52	Neil Lomax	3153	1981	1988	74.9	34	1.11	-0.02
53	Bill Munson	1982	1964	1979	70.3	76	1.11	0.07
54	Marc Bulger	3171	2002	2009	69.8	82	1.11	0.08
55	Dave Krieg	5311	1980	1998	72.3	51	1.10	0.03
56	Brian Sipe	3439	1974	1983	70.9	67	1.10	0.05
57	Gary Danielson	1932	1976	1988	71.2	62	1.10	0.04
58	Warren Moon	6823	1984	2000	71.2	63	1.09	0.03
59	Archie Manning	3642	1971	1984	66	115	1.09	0.13
60	Joe Theismann	3602	1974	1985	72.3	52	1.09	0.01
61	Jim McMahon	2573	1982	1996	69.7	85	1.09	0.06
62	Russell Wilson	3261	2012	2018	78.4	21	1.08	-0.12
63	Jim Harbaugh	3918	1987	2000	67.3	102	1.08	0.10
64	Steve McNair	4544	1995	2007	70.3	77	1.08	0.04
65	Trent Green	3740	1997	2008	73	48	1.08	-0.02
66	Steve DeBerg	5024	1978	1998	67.3	103	1.08	0.09
67	Tom Flores	1715	1960	1969	73.1	46	1.08	-0.02
68	Charlie Conerly	2833	1948	1961	75.7	28	1.08	-0.08
69	Elvis Grbac	2445	1994	2001	68.5	94	1.07	0.06
70	Craig Morton	3786	1965	1982	72.6	49	1.07	-0.03
71	Carson Palmer	6307	2004	2017	69.8	83	1.07	0.03
72	Billy Kilmer	2984	1961	1978	72.3	50	1.06	-0.03
73	Mark Brunell	4640	1994	2011	71.9	56	1.06	-0.02
74	Tim Couch	1714	1999	2003	63.2	153	1.06	0.15
75	Wade Wilson	2428	1981	1998	66.9	105	1.06	0.07
76	Steve Bartkowski	3456	1975	1986	70.7	71	1.05	-0.01
77	Jon Kitna	4442	1997	2011	64.3	139	1.05	0.12
78	Lynn Dickey	3125	1971	1985	66.3	113	1.05	0.07
79	David Garrard	2281	2002	2010	69.9	80	1.05	0.00
80	Jim Everett	4923	1986	1997	68.8	91	1.05	0.02
81	John Hadl	4687	1962	1977	71	66	1.05	-0.02
82	Roman Gabriel	4498	1962	1977	73.6	40	1.04	-0.08
83	Sam Bradford	2967	2010	2018	64.3	140	1.04	0.10
84	Joe Namath	3762	1965	1977	68.7	93	1.04	0.01
85	Alex Smith	4941	2005	2018	67.8	96	1.04	0.03
86	Chris Chandler	4005	1988	2004	68.8	92	1.03	0.00
87	Boomer Esiason	5205	1984	1997	71.7	57	1.03	-0.06
88	Jeff George	3967	1990	2001	69.7	84	1.03	-0.02
89	Jay Cutler	4920	2006	2017	66.5	109	1.03	0.04
90	Jeff Hostetler	2338	1985	1997	70	79	1.02	-0.03
91	Norm Snead	4353	1961	1976	63.5	150	1.02	0.09
92	Ryan Tannehill	2911	2012	2018	65.3	122	1.02	0.06
93	John Elway	7250	1983	1998	70.4	74	1.02	-0.05
94	Matthew Stafford	5405	2009	2018	67.7	98	1.02	0.00
95	Randall Cunningham	4289	1985	2001	72.1	54	1.02	-0.09
96	Neil O'Donnell	3229	1991	2003	71.1	65	1.01	-0.07
97	Matt Hasselbeck	5330	1999	2015	66.8	106	1.01	0.01
98	Bobby Layne	3700	1948	1962	70.1	78	1.01	-0.05
99	Andy Dalton	3921	2011	2018	67.7	97	1.01	-0.01
100	Daryle Lamonica	2601	1963	1974	76.5	26	1.01	-0.18
101	Eddie LeBaron	1796	1952	1963	65.1	128	1.01	0.04
102	Marcus Mariota	1605	2015	2018	66.5	111	1.01	0.01
103	Erik Kramer	2299	1987	1999	65.8	118	1.00	0.02
104	Mike Livingston	1751	1968	1979	65.1	131	1.00	0.04
105	David Carr	2267	2002	2012	60.7	166	1.00	0.12
106	Earl Morrall	2689	1956	1976	73.4	43	1.00	-0.13
107	Tommy Kramer	3651	1977	1990	66.4	112	1.00	0.00
108	Vince Ferragamo	1615	1977	1986	63.6	149	1.00	0.06
109	Joe Flacco	5670	2008	2018	64.1	142	1.00	0.05
110	Jay Fiedler	1717	1995	2005	64.8	134	0.99	0.03
111	George Blanda	4007	1949	1975	67.4	101	0.99	-0.03
112	Phil Simms	4647	1979	1993	70.6	72	0.99	-0.09
113	Derek Carr	2800	2014	2018	65.8	117	0.99	0.00
114	Rodney Peete	2346	1989	2004	62.3	156	0.98	0.07
115	Steve Beuerlein	3328	1988	2003	69.8	81	0.98	-0.09
116	Frank Ryan	2133	1958	1970	75.1	31	0.98	-0.19
117	Jake Delhomme	2932	1999	2011	66.6	108	0.97	-0.03
118	Jason Campbell	2518	2006	2014	64.9	133	0.97	0.00
119	Don Majkowski	1905	1987	1996	63.9	147	0.97	0.01
120	Charley Johnson	3392	1961	1975	67	104	0.97	-0.05
121	Stan Humphries	2516	1989	1997	65.2	124	0.96	-0.02
122	Mark Rypien	2613	1988	2001	69.4	88	0.96	-0.10
123	Donovan McNabb	5374	1999	2011	71.3	61	0.96	-0.14
124	Nick Foles	1581	2012	2018	66.7	107	0.96	-0.05
125	Richard Todd	2967	1976	1985	62.4	155	0.96	0.03
126	Bill Nelsen	1905	1963	1972	68.9	90	0.95	-0.11
127	Don Meredith	2308	1960	1968	71.6	59	0.95	-0.16
128	Jack Kemp	3073	1957	1969	62.2	157	0.95	0.03
129	Vinny Testaverde	6701	1987	2007	64	143	0.95	-0.01
130	Bill Kenney	2430	1980	1988	69.1	89	0.95	-0.11
131	Babe Parilli	3330	1952	1969	65.7	119	0.95	-0.05
132	Drew Bledsoe	6717	1993	2006	65.1	130	0.95	-0.04
133	Case Keenum	1844	2012	2018	61.7	160	0.95	0.03
134	Josh McCown	2628	2002	2018	61	165	0.94	0.03
135	Eli Manning	7972	2004	2018	65.2	125	0.94	-0.05
136	Jim Plunkett	3701	1971	1986	65.1	127	0.94	-0.05
137	Terry Bradshaw	3901	1970	1983	70.3	75	0.94	-0.16
138	Jim Zorn	3149	1976	1987	64	144	0.94	-0.03
139	Jake Plummer	4350	1997	2006	62	158	0.93	0.00
140	Kyle Orton	2712	2005	2014	63.9	146	0.93	-0.04
141	Ryan Fitzpatrick	4285	2005	2018	61.3	163	0.92	0.00
142	Jeff Blake	3241	1992	2005	66.5	110	0.92	-0.10
143	Dan Pastorini	3055	1971	1983	59.9	170	0.92	0.03
144	Jim Hart	5076	1966	1984	66.1	114	0.92	-0.09
145	Jameis Winston	1922	2015	2018	64.7	135	0.92	-0.07
146	Charlie Batch	1604	1998	2012	65.1	126	0.92	-0.08
147	Chad Henne	1959	2008	2018	57.5	177	0.92	0.07
148	Byron Leftwich	1605	2003	2012	64.5	138	0.91	-0.07
149	Ron Jaworski	4117	1974	1989	67.8	95	0.91	-0.14
150	Andrew Luck	3290	2012	2018	67.5	100	0.91	-0.14
151	Bubby Brister	2212	1986	2000	63.5	151	0.91	-0.06
152	Eric Hipple	1546	1980	1989	61.6	161	0.91	-0.02
153	Kordell Stewart	2358	1995	2005	59.2	174	0.91	0.02
154	Joe Ferguson	4519	1973	1990	65	132	0.90	-0.10
155	Scott Mitchell	2346	1991	2001	64.6	137	0.90	-0.09
156	Chris Miller	2892	1987	1999	65.4	121	0.90	-0.11
157	Steve Grogan	3593	1975	1990	65.9	116	0.90	-0.12
158	Matt Cassel	2684	2005	2018	60.4	169	0.88	-0.03
159	Steve Bono	1701	1985	1999	64.7	136	0.88	-0.11
160	Colin Kaepernick	1692	2011	2016	67.6	99	0.88	-0.18
161	Cam Newton	3892	2011	2018	65.1	129	0.87	-0.14
162	Trent Dilfer	3172	1994	2007	58.2	175	0.87	0.00
163	Doug Flutie	2151	1986	2005	65.6	120	0.87	-0.16
164	Aaron Brooks	2963	2000	2006	65.2	123	0.86	-0.16
165	Ed Brown	1987	1954	1965	63.3	152	0.86	-0.12
166	Jack Trudeau	1644	1986	1995	55.1	183	0.85	0.03
167	Tobin Rote	2907	1950	1966	63.9	145	0.85	-0.14
168	Josh Freeman	2048	2009	2015	59.8	172	0.85	-0.06
169	Dave Brown	1634	1992	2001	56.6	179	0.85	0.00
170	Kerry Collins	6261	1995	2011	60.6	167	0.84	-0.09
171	Tony Banks	2356	1996	2005	61.4	162	0.84	-0.11
172	Mike Tomczak	2337	1985	1999	59.9	171	0.84	-0.08
173	Kyle Boller	1519	2003	2011	55.1	184	0.84	0.01
174	Marc Wilson	2081	1980	1990	59.5	173	0.84	-0.08
175	Mike Phipps	1799	1970	1981	53.2	188	0.83	0.04
176	Joey Harrington	2538	2002	2007	55.3	181	0.82	-0.01
177	Gus Frerotte	3106	1994	2008	61.9	159	0.82	-0.15
178	Blake Bortles	2632	2014	2018	57.8	176	0.81	-0.07
179	Michael Vick	3217	2001	2015	64.3	141	0.80	-0.22
180	Cotton Davidson	1752	1954	1968	60.5	168	0.80	-0.15
181	Mark Malone	1648	1980	1989	54.3	186	0.79	-0.04
182	Mark Sanchez	2320	2009	2018	54.9	185	0.78	-0.06
183	Billy Joe Tolliver	1707	1989	1999	57.3	178	0.77	-0.12
184	Rick Mirer	2043	1993	2003	52.4	189	0.77	-0.02
185	Rex Grossman	1562	2003	2012	55.8	180	0.76	-0.11
186	Jay Schroeder	2808	1985	1994	62.9	154	0.73	-0.28
187	Doug Williams	2507	1978	1989	63.7	148	0.73	-0.31
188	Mike Pagel	1509	1982	1993	55.3	182	0.71	-0.16
189	Derek Anderson	1674	2006	2018	53.6	187	0.66	-0.20

In some ways, it’s that last column that is most interesting to me. Completion percentage is significantly overstated in the passer rating formula, so if a player is much higher in completion percentage than in their average of the other three metrics, it’s very likely that passer rating overstates their true value. So let’s break the groups into those whose passer ratings are inflated by strong completion percentages and those whose ratings are deflated by weak completion percentages.

Boosted By High Completion Percentages

Frank Tripucka is your leader here, followed by Sammy Baugh, Ken Stabler, Chad Pennington, Troy Aikman, Brian Griese, Bart Starr, Drew Brees, Tim Couch, and John Brodie. It’s an interesting group of players: Tripucka and Couch still have below-average passer ratings (66.7 is average) despite strong completion percentages, while Griese, Brodie, and Aikman were basically average other than their stellar completion percentages. Meanwhile, Stabler and Pennington were efficient passers who happened to be best at completion percentage, and that goes triple for guys like Baugh, Brees, and Starr. Pennington was a very good quarterback, but his 29th-place ranking in passer rating is more a function of how the formula tips the scales in favor of high completion percentage.

Harmed By Low Completion Percentages

Doug Williams is the biggest outlier here, and he had a very low sack rate which helps to explain his low completion percentage. Other players who were much better in Y/A, TD%, and INT% than completion percentage include Jay Schroeder, Michael Vick, Derek Anderson, Frank Ryan, Daryle Lamonica, Colin Kaepernick, Aaron Brooks, Don Meredith, Mike Pagel, and Terry Bradshaw.

Vick is another interesting choice. Did you know that from 2001 to 2013 he led all players in yards per completion but he ranked 46th out of 50 passers in completion percentage? Vick also replaced a lot of easy, 5-yard completions with 5-yard scrambles (or longer), which artificially deflated his completion percentage. Some of that probably applies to Colin Kaepernick, too, and his case is even more interesting because of his remarkably low interception rate juxtaposed against his low completion percentage. Lamonica and Ryan were two HOF caliber passers who are underrated when you examine completion percentage: how much differently would we view their careers if they had slightly lower Y/C averages and higher completion percentages?

What stands out to you?

Tagged as: Completion Percentage, Passer Rating

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