Evaluating running backs has become a tricky business in recent years.
It wasn't long ago that everybody was looking for the new Walter Payton—a complete running back that could carry the load while also being trusted to catch passes, block like a fullback and protect the quarterback—but that isn't the case anymore.
There are no longer many true every-down runners, and fewer still season-long workhorses that will see the kind of workload past greats received.
For evidence of this, look at Emmitt Smith, who averaged 324 carries per season for his first 10 years. That is more than any other running back last season outside of Maurice Jones-Drew, who was forced into so many carries as much by the quarterback situation in Jacksonville as anything else.
Only one other runner had more than 300 carries last season (Atlanta's Michael Turner with 301), and the recent talk has been of how his workload needs to be shared with Jacquizz Rodgers.
The days of the do-everything running back are fading, so what we are now looking at is a league full of specialists, each of whom has carved out their own special niche in an offense.
When analyzing running backs today, you aren't simply looking at a checklist of skills to see if that player can be a total player. You're looking at the skills he has and trying to project those skills into offenses in the NFL to see how that player could be used by particular teams.
One team's trash becomes another team's treasure, because they are better prepared to make use of that player's unique skill set.
We're going to look at certain traits and how they have helped some players succeed in particular situations.
Holes in the NFL don't stay open for long. You've got to be able to accelerate in quick order and burst through gaps when they appear.
One of the things that makes Adrian Peterson such a dangerous runner is the time in which he can hit top gear. This is a crucial trait for an NFL running back because you're not always going to have the blocking needed for those few crucial yards.
You hear about running backs only being able to pick up the yards that are there. Thomas Jones, for example, won't make anything happen on his own but will always follow his blocking and pick up as many yards as they allow him to.
NFL teams want runners who will do that but can also get yards on their own when the blocking breaks down. When they find a hole closed in front of them, the ability to reroute and accelerate to full speed in an instant is crucial.
This is what makes Peterson so dangerous, because when he is moving at his top speed, he is a load to bring down.
By the time a runner gets to the NFL level, you assume they can all do what Thomas Jones does, acting as a calibration tool for offensive lines by just following the blocking until the yards run out. But what separates those guys from the players that can make it at this next level is that burst and acceleration to make plays themselves.
Almost without exception, top runners at the NFL level have a burst to their play, and those that don't (Michael Turner, for example) have another trait in its stead.
In Turner's case, while he may not be able to accelerate back to top speed in an instant, he has an impressive ability to keep rumbling forward through contact. He is rarely stopped cold with a hit.
Maximizing the yards on a particular run is often less about being able to outrun defenders to a particular spot or force through tackles in order to gain extra yards. It's more about having the vision to cut to open space in the first place.
If a running back can see where the space is and make the move to it early, he can spring himself for additional yardage with a single move that can break the whole play open.
This is especially important in two key areas: in zone blocking schemes and at the second level.
You hear the term "one-cut runner" in conjunction with zone blocking a lot. It is the defining characteristic of those runners in that scheme, but it relies on vision.
In zone blocking schemes, the offensive line moves the line of scrimmage in one direction laterally, with each lineman responsible for an area rather than a man. Usually, the weak-side blockers will attempt to cut their defenders to the ground to open up a hole in the defense that the running back can then cut into to make yards.
The job of the running back is to be patient with the football as this blocking develops. Then, he must have the vision to see the hole and cut into the space quickly to pick up yardage.
Arian Foster has proven to be an exceptional one-cut running back in recent seasons as the Houston Texans executed the league's finest example of a zone blocking scheme. Foster has been able to use his vision to gain impressive yardage behind that unit.
The second area where vision is crucial is at the second level of the defense. Once a runner gets through the line of scrimmage, they can often break a play wide open if they have the vision to immediately locate the space and cut towards it.
From that point, they are often facing defenders coming hard towards the line of scrimmage, and an early cut can leave them in no man's land. DeMarco Murray showed excellent ability to do this last season, as he can break through to the second level and make an early cut towards space, leaving safeties struggling to match his change of direction.
In a league that has become ever more specialized, one way of stressing a defense is by having a player that can't be matched up with in the huddle.
By that I mean having a player that can be on the field for both heavy run formations and pass-only situations. This creates a serious problem for defenses who have to work out how to treat that player before they ever see how the offense is going to line up.
Danny Woodhead, for instance, put up massive numbers in college but was seen as too small to do that job in the NFL. The New York Jets initially tried to turn him into their version of Wes Welker as a slot receiver, but they eventually bailed on that experiment and cut him loose.
New England picked him up and realized the problem he could pose to NFL defenses. Woodhead has the receiving skills to be a slot receiver just like Wes Welker, but he also has the experience and ability to run the ball, even between the tackles.
On any given play, they can line him up in I-formation and pound the football, or they can line him up as a wide receiver. Pairing him with a similar matchup problem in Aaron Hernandez makes the New England offense a defense's worst nightmare.
This versatility as a receiver is crucial in today's NFL. It's a passing league, so forcing teams to cover receivers while also respecting that player's ability to run gives offenses an enormous advantage.
There are plenty of players that would not hold up over a traditional 300-carry season, but if they can strike a balance in the right offense with their running and receiving skills, they will be seen as a dual threat.
Players can not only make an NFL roster today, but also become crucial contributors on offense if they have the receiving skills to supersede the limits of their durability in the run game. Danny Woodhead and Darren Sproles are just two examples of this, but there are more coming into the league every year.
If there's one thing that can keep a talented player on the sideline these days, it's not being able to contribute in pass protection.
Running backs don't necessarily have to be Walter Payton when it comes to blocking, but they need to be able to read a defense, pick up the right guy on the blitz and at least make it difficult for a defender to get through to the quarterback.
It's no coincidence that some of the best and most durable backs in recent years have been some of the best in this area of the game.
Buffalo's Fred Jackson really came alive as a part of the Bills offense once he improved his pass protection. Once a real weak point of his game, Jackson may have been the best blocking RB in the league before he was injured last season.
Maurice Jones-Drew has also developed a long highlight reel of blitz pickups over the years.
The key to this area of the game is more mental than it is physical. Nothing will get you sent to the bench quicker than failing to even pick up the correct guy in pass protection. Coaches can forgive players getting beaten on the block, but they are far less ready to forgive mental errors that will give a defender a clean run to the quarterback.
The ability to spot the right guy, step up and stick their nose in on the block is hugely important for running backs in this league. This is especially true for teams that will run play-action and face a lot of heavy fronts or those that are going to be facing the blitz heavily in a game.
Some people won't care if their runner can block if he runs the ball like Adrian Peterson, but Peterson himself has been left off the field in key situations because of the issues he has had in pass protection.
However good the runner is, the quarterback remains the most important position on the field, and coaches won't stand for a player who allows free runs to their signal-caller because he can't pick up the blitz.
The last player that was able to successfully ignore holes on a regular basis to try and make things happen on his own was Barry Sanders. Since then, many runners have tried, but every one of them finds that you just can't combat NFL defenses that way anymore—they're too fast and too organized.
Reggie Bush has always had huge talent, but he has rarely had the discipline to take what was there and forgo trying to bounce it outside for the big play on every run.
Runners don't just need the vision to find the space, but they also need to understand the situation and when the five yards in front of them are the best option. Being on offense is about staying ahead of the chains, not trying to score on every play.
It is no coincidence that Bush enjoyed something of a renaissance in Miami when he began to take what was there and stick to the play that was drawn up, rather than trying to chase the elusive bounce-out run to the end zone.
Players at high school and the college level are used to being able to bounce the ball outside and outrun inferior athletes to pay dirt, but in the NFL, everybody is a fantastic athlete. At this level, you need to be able to see when running straight ahead for positive yardage is your best bet, while also recognizing those moments in which you can cut to daylight.
It wasn't long ago that runners needed all of these skills to be viable in the NFL, but these days you can be a successful player if you have one or two of them and find the right offense to work in.