You've got players like Alfred Morris, Doug Martin and Frank Gore that check-in at 5'9". While football is known as a sport that's looking for the biggest, baddest players around at that particular position, that doesn't always mean height when talking running backs.
We're going to take a look at how you'd design the perfect running back in today's NFL. Considering the season that Adrian Peterson had last year, it's hard not to just take a look at him and say, "This! This is what the perfect NFL running back is supposed to look like."
Let's start with height.
You don't want the player to stand too tall in the backfield because it makes him easier to find for the defensive players. Shorter players can "hide" behind the taller offensive linemen. You also want to have a low center of gravity and make it easier to get underneath the pads of defenders looking to make a tackle.
You'll see players like Morris, Trent Richardson, Ray Rice, Maurice Jones-Drew and Frank Gore that have consistently shown that height isn't as important a factor for a running back as it could be for some other positions. In many cases, like for the players above, being shorter has actually been a benefit for them. They're able to get underneath defenders and use their lower body strength to always fall forward.
Shorter players also tend to be "stockier" and pack a punch with a bowling ball-type mentality. Shorter legs also mean shorter strides and an ability to change directions quicker than a 6'2" back like you'd see from Steven Jackson.
If you had to design the perfect height for an NFL running back it would be 5'10".
Now let's look at weight.
Weight is a difficult one to determine, because it matters where the weight is distributed. Ideally, you'd want a thick lower-half that would allow the running back to break arm tackles when running through the box, and the upper-body strength to not bounce off defenders and have their momentum disrupted so easily.
You see featured NFL backs today like Jamaal Charles and Chris Johnson that weight under 200 pounds. Both of these players finished in the top 10 in number of carries for 2012, but there are questions surrounding both of these players and their ability to consistently take hits and still maintain their speed and quickness, which is what makes them both so special.
The second-tier of running backs in terms of weight would be guys like Matt Forte, Reggie Bush, CJ Spiller and LeSean McCoy. These four players are just over 200 pounds but are still considered among the "more quick than powerful" mold of running backs.
All four of these players have had injury concerns, and ideally you'd want a player with just a bit more muscle and physicality to pick up the tough yards running between the tackles.
Guys like Peterson, Morris, Richardson, Foster and Marshawn Lynch sit in the 215-225-pound range. This seems to be the ideal weight for a running back. But again, it's more about the distribution of the weight and the muscle-mass involved with the player than strictly just their weight.
Strength vs. Speed
If this were a 'create a player' page in a video game, you'd just make the strongest, fastest player possible. That's an easy thing to say when trying to put together the ideal running back.
The most important physical skill set an NFL running back can have is quickness. You don't have to be a burner to be an effective running back. Jackson has never been a burner, but he's shown himself to be quick enough that, combined with his size and strength, he offers more than enough to be a featured back.
Rice is more quick than fast, and the same can be said for Morris, Gore and Stevan Ridley. A running back needs to be able to get through a hole as soon as possible. Whether he then has the open-field speed to not get caught from behind is another thing.
Charles, Spiller and Peterson have the speed to break open big runs in the open field. Peterson is special because he possesses that speed along with the strength and physical stature to take hits running up the middle and still drive forward.
The perfect NFL running back would possess enough muscle-mass and strength that he can withstand hits from linebackers meeting him in the hole and still find ways to fall forward. That's extremely difficult to consistently do by running backs that fit those first two tiers at around 205 pounds and lower.
The player doesn't have to have first-class speed or be the strongest player on the field. In fact, too much of one of those things could affect the other. It's difficult (unless you're AP) to have world-class speed AND pack enough muscle mass to absorb hits inside the box. Adding that muscle would just slow you down.
But if you've got too much speed and that leads to not having adequate strength to take hits, then you're looking at injuries and situational duty. It takes the right combination of both.
The next most important thing in designing the perfect NFL running back is they have to have the athletic fluidity out in space to be a factor in the passing game. They need to be able to take on pass-rushers in pass protection, and they need to be comfortable catching the football.
If you're not able to do those things, then you're limiting yourself to a two-down running back in today's pass-happy NFL.
You might have read this and realized it's describing Adrian Peterson pretty well, and there's a lot of truth in that. If I had to design the perfect NFL running back he'd look real close to Peterson, but would be just a little bit shorter so he could hide better behind the line of scrimmage.
That's getting awfully picky, but we're looking at ideal here. It takes a pretty special player to lead the league in attempts (348), runs over 20 yards (27) and rushing yards per attempt (6.0) like Peterson did last year. It's why this "ideal" closely resembles the player he is right now.