A couple of weeks ago, Jason Lisk wrote this post over at the PFR.com blog on the likelihood of Frank Gore becoming the 49ers all time leading rusher. In that post, he referred to another post from three years ago, which looked at the probability of certain players breaking Emmitt Smith’s career rushing record. Two years ago, I thought that LaDainian Tomlinson had the best shot at breaking Emmitt’s record of anyone currently playing. But, he seems to be slowing down quite a bit recently. With these posts in mind, I started to think that the changes in the NFL game may actually make it less likely for any RB to break Emmitt’s record.
In the last 4-5 years, teams have really used multiple running backs more than I can remember. Twenty years ago, if a team tried didn’t have a feature running back, they usually didn’t have a good running game. These days, the best running teams have multiple running backs that can be feature backs (Giants, Panthers, Titans, and Cowboys to name a few). Because of that, I wondered if it was becoming less likely that a running back would actually get enough opportunities to break the record. So, I decided to take a look at the average yardage per year of all running backs with over 1150 yards since 1978 and see if the averages are trending downward at all.
Why 1978, and why 1150 yards? Well, originally, I was going to look at all players with over 1000 yards per season in NFL history. But, there were only 97 instances of a running back going over 1000 yards from 1920 to 1977. Since 1978, there have been 420 instances of backs going over 1000 yards. In 1978, the NFL went from 14 game to 16 game seasons, so I made an adjustment to the required yardage to see if that made much difference. I calculated the adjustment by dividing 1000 by 14, which came out to be about 71 yards/game. With two additional games, 1150 seemed like a nice round number, rather than sticking with 1142. Regardless, there are still 235 instances of a player gaining 1150 yards or more from 1978 to 2008. So, it became clear that any data from before 1978 would not be useful in this analysis anyway.
Pulling my data from Pro Football Reference‘s Player Season Finder, for player with 1150 rushing yards or more in a given year, I calculated the average rushing yards per year, average yards per attempt, and average yards per game. In the interest of full disclosure, I will admit that my yards/attempt and yards/game calculations were averages of averages. That is, I did not sum the total yards for all players and divide by the total number of attempts or games. I just averaged the values of each players’ numbers for the given year. While not completely mathematically accurate, I think it will work for my objective here. The results for the years 1978-2008 are shown in the table below.
|Year||Count||Avg Yds/Yr||Avg Y/A||Avg Y/G|
No players broke 1000 yards in 1982, due to the strike shortened year, and only 2 did in 1987, the other strike shortened year. However, from 1978 to 1997, there was only a single season, 1984, where 10 or more players broke 1150 yards rushing. Beginning in 1998, we had a string of 9 consecutive years with over 10 players reaching or exceeding that mark. But, in 2007 and 2008, only 9 reached it each year.
To make this data a little more easily readable, I have created three separate charts graphing the average rushing yards per year, average yards per attempt, and average rushing yards per game against the corresponding years. This should show us graphically if there is a trend downward or upward in any of these. First, the Average Yards per Year:
Next, Average Yards per Attempt:
And, finally, Average Yards per Game:
Well, none of these really show a clear trend one way or the other. So, in terms of an intrinsic change in how the game is played, year to year, there does not appear to be evidence of it yet. But, my data is not yet complete. Since this data did not give me a clear indication as to whether or not a player may have a good shot at breaking the record, I decided to go back again to the historical record. Again using Pro Football Reference‘s Player Season Finder, I ran a few queries on how many players have rushed for a given amount of yards by a certain age.
First, I queried players that had rushed for 3000 or more yards by age 22. If you click the link, you see that there are only two players, Edgerrin James and Clinton Portis. Next, I queried players who had 6000 yards by age 25 (I tried age 24 first, but there are none). There are seven players in this category (listed in order of rank): Emmitt Smith, Walter Payton, Barry Sanders, Jim Brown, Clinton Portis, Jerome Bettis, and Edgerrin James. Then, since Smith, Payton and Sanders had close to or more than 7000 yards by age 25, I queried players with 8000 yards by age 26. As you can see by clicking, Smith, Sanders, and Payton were the only ones. Finally, I queried the number of players with 10,000 yards by age 27. Only Barry Sanders and Emmitt Smith qualified there. Although LaDainian Tomlinson and Eric Dickerson gained more yards in their first 7 seasons than Sanders and Smith, LT was 22 his rookie season and Dickerson was 23.
Having looked at this data, although many teams appear to be using multiple backs more than in some years past, as far as I can tell, it’s no less likely than it was before that someone could come along and break Emmitt’s record. The key, before everything else, appears to be that they must be 21 years old their rookie season, and they must be productive and avoid injuries early in their career. This conclusion also lines up with this post on the PFR blog, which I just came across today. So, it looks like I’m following up on something that was done earlier, but my data here does add to and support earlier conclusions.