SITE NEWS: We are moving all of our site and company news into a single blog for Sports-Reference.com. We'll tag all PFR content, so you can quickly and easily find the content you want.

Also, our existing PFR blog rss feed will be redirected to the new site's feed.

For more from Chase and Jason, check out their work at Football Perspective and The Big Lead.

# Pro Football Reference Blog

## What great running back was most helped by his offensive line? Part II

Posted by Doug on August 5, 2008

In yesterday's post I used a variety of metrics to determine which running back was most helped by his offensive line. All of them were lacking in one way or another, so I am going to make a more sophisticated effort with this post. Will it be a more accurate effort? I'll let you decide.

First I used my Approximate Value method to construct an aging curve for offensive linemen. This topic is itself enough for a whole post or more, but for now I'll skip it and just show you the curve.

```Age  PctOfPeak
============
21 => 0.48
22 => 0.48
23 => 0.57
24 => 0.81
25 => 0.93
26 => 0.97
27 => 1.00
28 => 1.00
29 => 0.97
30 => 0.91
31 => 0.90
32 => 0.88
33 => 0.78
34 => 0.76
35 => 0.77
36 => 0.63
37 => 0.62
38 => 0.62
39 => 0.62
40 => 0.62
```

These numbers are fractions of peak AV. So according to this, a typical lineman has a pretty flat peak from age 26 to 29. He loses about 10% of that value by his age 30 season, and another 10ish percent by age 33. By age 40, if he's still around, he's about 60% of the player he was at his peak.

Next, I take every offensive lineman and define his Peak AV as the average of his three (not necessarily consecutive) best seasons.

Then, for each season, I multiply his peak AV by the appropriate age multiplier and assume that's about how good he was in that year.

The idea here is to get an estimate for how good a lineman was in each year of his career without making it so directly tied to the quality of his team and the honors and awards that he happened to win in just that year.

Alright, so now we've got a quality estimate for every lineman for every year. And, for all its potential faults, I do think it successfully addresses some of the concerns of the metrics we used yesterday: Anthony Munoz is distinguished from Frank Winters; non-pro-bowlers are not counted as useless; a decrepit old Bruce Matthews is not counted as equal to a prime Bruce Matthews.

Below is the same list of 100 running backs from yesterday, this time sorted by the (carry-weighted) average estimated (as above) quality of all five starting offensive linemen on each team they played for:

```Jim Brown            54.99
Calvin Hill          51.96
Jim Taylor           49.74
Mark van Eeghen      49.19
Chuck Foreman        48.32
Mike Garrett         47.52
Lenny Moore          47.13
Roger Craig          46.76
Larry Csonka         45.83
```

```Sam Cunningham       45.15
James Brooks         44.53
Terrell Davis        44.35
Robert Smith         44.09
Lydell Mitchell      43.95
Wendell Tyler        43.55
Priest Holmes        43.34
Leroy Kelly          42.92
Bill Brown           42.04
Emmitt Smith         41.83
Edgerrin James       41.62
Tony Dorsett         41.35
Lawrence McCutcheon  41.34
Earnest Byner        41.12
Thurman Thomas       40.85
Emerson Boozer       40.62
Ken Willard          40.62
Rick Casares         40.45
Delvin Williams      40.38
William Andrews      40.38
Gerald Riggs         40.27
Pete Johnson         40.25
Larry Jr. Brown      40.16
Mike Pruitt          40.09
Franco Harris        39.74
Marshall Faulk       39.44
Eric Dickerson       39.35
Eddie George         39.28
Hugh McElhenny       39.03
Freeman McNeil       39.02
Corey Dillon         38.88
Shaun Alexander      38.84
Dick Bass            38.70
Neal Anderson        38.24
Herschel Walker      37.93
John Riggins         37.77
Rudi Johnson         37.72
Ricky Watters        37.43
Ahman Green          36.86
Barry Sanders        36.80
John Henry Johnson   36.78
Marcus Allen         36.69
Clem Daniels         36.67
Jerome Bettis        36.67
Greg Pruitt          36.66
Joe Cribbs           36.64
George Rogers        36.57
Chuck Muncie         35.80
Charlie Garner       35.55
Curt Warner          35.36
Joe Morris           35.13
Wilbert Montgomery   35.12
Kevin Mack           35.11
John Brockington     35.03
Rodney Hampton       34.83
Terry Allen          34.80
Duce Staley          34.80
Clinton Portis       34.65
Fred Taylor          34.44
Curtis Martin        34.27
Don Perkins          34.18
Jim Nance            34.09
Natrone Means        33.75
Garrison Hearst      33.70
Antowain Smith       33.70
Jamal Anderson       33.68
Chris Warren         33.43
Jamal Lewis          33.26
Earl Campbell        33.03
O.J. Simpson         33.03
Ottis Anderson       32.82
Sammy Winder         32.55
James Stewart        32.26
Walter Payton        32.23
Stephen Davis        32.02
Ricky Williams       31.94
Billy Sims           31.20
Deuce McAllister     31.16
Floyd Little         31.14
Ollie Matson         30.57
Marion Butts         30.41
Tiki Barber          30.38
Thomas Jones         30.36
Mike Alstott         29.50
Warrick Dunn         29.31
Dexter Bussey        28.94
Michael Pittman      27.54
Travis Henry         27.19
James Wilder         25.76
```

So what do we think of this list? I'll just make a couple of observations and then turn it over to you in the comments.

1. Emmitt Smith drops substantially compared to his placement on yesterday's lists. This method is essentially saying, "Yes, I know Emmitt played with a ton of pro bowl linemen, but c'mon, I ain't counting Mark Tuinei. Or a mid-30s Ray Donaldson or Nate Newton." Do you agree? I do.

2. Edgerrin James's appearance near the top of this list is interesting, considering he was in the bottom half of yesterday's lists. This is primarily because his Colt career coincided perfectly with the (assumed) primes of Jeff Saturday and Tarik Glenn, and the method assumes Glenn and Saturday were/are very good. James's time in Indy also featured the (assumed) peak seasons of some other solid linemen like Ryan Diem, Adam Meadows, and Rick DeMulling. [Random trivia: Edgerrin James has never played on a team with a starting lineman over age 30.]

Of course, AV only considers those guys to be solid linemen because they were multi-year starters on a great offense. This makes me suspicious that I haven't successfully eliminated the problem with using AV for this study that I mentioned yesterday.

Still, I think this is probably the best list of the four. Well, if it weren't for the fact that the process by which it was created is hopelessly complicated, I would think it was the best of the four.

This entry was posted on Tuesday, August 5th, 2008 at 4:16 am and is filed under Approximate Value, General. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.