TUSCALOOSA, AL - SEPTEMBER 17:  Running back T...

How long can Trent Richardson expect to play in the NFL?

The topic comes up every year: how long is the average football player’s career?  People are particularly interested in the length of an NFL running back’s career, since it seems that injuries often cut their careers short.  This is often given as 4-5 years, with some estimates coming in as low as 2.5 years.

As is often the case, methodology is going to be very important.

Perhaps the worst methodology I have ever seen was looking at the current starting running backs and calculating the mean number of years they have been in the NFL.  However, this uses mid-career numbers and is going to underestimate the reality.  Would you take a 2 year old, 45 year old, and 75 year old and simply use the mean of their ages (40.67) and declare this to be the average life span?  Of course not – nor should you use mid-career numbers to calculate the average length of career.

The second issue is the decision of whom to include.  Do we include ALL NFL running backs, even the guy from Kosmo State who went in the 7th round and narrowly held onto a roster spot for a year before getting cut?  This guy’s career was cut short by lack of talent, not by injury.  We need to separate the wheat from the chaff and determine the average career length of a GOOD NFL running back.  I doubt that the casual fan is too concerned about how long her team’s third string back will kick around the league.

My methodology

There are two decisions to be made with the data.  The first is how to quantify “good”.  I’m going to take the years 1991-2010 and look at running backs who finished in the top 20 in the league in rushing yards at least once during that twenty year span.  My thought is that if you’re a good running back – the type that carries a team – you’re going to land in the top 20 at some point.  Maybe not every year, but at least once.  This is going to miss some situations like guys who are part of a tandem backfield for their entire career, but it should at least provide a decent sample size to work with.  I am excluding active players (defined as players who played in 2011), because of the problem with mid-career numbers.  Rushing yards isn’t a perfect barometer, but it should be fairly sound.

The second decision is what is meant by “length of career”.  Years can be messy – if a guy plays 9 games, does he get credit for a year?  I decided to just scrap the idea of years and go with games instead.

The data

Twenty years of top 20 lists means 400 names.  However, many players made the list multiple times.  There were 150 unique names on the list.  40 of these players are active, leaving 110 retired players in this group.  Here is the list, in order of most to fewest games played.

Player Games
Emmitt Smith 226
Marcus Allen 222
Earnest Byner 211
Jerome Bettis 192
Herschel Walker 187
Thurman Thomas 182
Warrick Dunn 181
Marshall Faulk 176
Curtis Martin 168
Chris Warren 162
Anthony Johnson 159
Mike Alstott 158
Tiki Barber 154
Troy Hambrick 154
Barry Sanders 153
Fred Lane 153
Michael Pittman 151
Corey Dillon 150
Craig Heyward 149
John L. Williams 149
Ahman Green 148
Edgerrin James 148
Charlie Garner 147
Eric Dickerson 146
Dorsey Levens 144
Leroy Hoard 144
Ricky Watters 144
Stephen Davis 143
Eddie George 141
Bernie Parmalee 134
Antowain Smith 131
Jamal Lewis 131
Terry Allen 130
Fred Taylor 126
Garrison Hearst 126
Harold Green 124
Tyrone Wheatley 124
Shaun Alexander 123
Adrian Murrell 122
Brian Westbrook 121
Neal Anderson 116
Lamar Smith 115
Duce Staley 114
LaMont Jordan 114
Reuben Droughns 114
Clinton Portis 113
Priest Holmes 113
Edgar Bennett 112
Ladell Betts 111
Harvey Williams 110
Lewis Tillman 109
Lorenzo White 107
Michael Bennett 107
Marion Butts 104
Rodney Hampton 104
Erric Pegram 103
Rodney Thomas 103
James Stewart 101
Dominic Rhodes 99
Gary Brown 99
Kevin Mack 99
Earnest Graham 98
Mario Bates 98
Mike Anderson 98
Robert Smith 98
Deuce McAllister 97
Rudi Johnson 95
Brad Baxter 94
Julius Jones 94
Justin Fargas 92
Reggie Cobb 92
Napoleon Kaufman 91
Mark Higgs 90
Travis Henry 89
Jamal Anderson 88
Natrone Means 88
Robert Delpino 88
Allen Pinkett 87
Anthony Thomas 87
Errict Rhett 86
Leonard Russell 85
Kevan Barlow 84
Rod Bernstine 84
Leroy Thompson 80
Willie Parker 79
Christian Okoye 79
Terrell Davis 78
Ronald Moore 77
Bam Morris 74
Johnny Johnson 72
Roosevelt Potts 71
Chris Brown 68
Cleveland Gary 68
James Allen 66
Blair Thomas 64
Kevin Jones 64
Barry Foster 62
Jerome Harrison 62
Abdul-Karim al-Jabbar 61
Gaston Green 58
Stacey Mack 58
Derek Brown 56
Raymont Harris 54
Tatum Bell 54
Olandis Gary 48
Domanick Williams 40
Reggie Brooks 40
Curtis Enis 36
Rashaan Salaam 33
Robert Edwards 28
Total  12034


Mean: 109.4

Median: 103.5

If we divide these numbers by a 16 game schedule, we get 6.8 years for the mean and 6.5 for the median.  However, it’s important to note that it’s pretty common for a player – in any sport – to get dinged up and miss a game every one in a while.  So even a generally healthy running back would generally stretch these games out over 7.5 – 8 years.  Only 27 of the 110 players in the group had a career of 80 games or fewer (5 full seasons).

Most likely, a running back with Trent Richardson’s pedigree can bank on an eight year NFL career.  Longer if he’s lucky, shorter if he’s not.

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