INDIANAPOLIS -- Over the past two seasons, the team with the best offense in the NFL on a per-game basis has had a little extra help. The "little" is in the part of the 5-foot-6 and generously listed 190-pound Darren Sproles, who helped the San Diego Chargers to a league-high 395.6 yards per game in 2010, then accounted for nearly 18 percent of the New Orleans Saints' league-high 7,474 yards in 2011 as a rusher and a receiver, achieving balance with 87 rushes and 86 catches. (Both teams placed sixth in the years before and after Sproles.)
Many have discussed the X's and O's of why Sproles has been successful, namely his ability in space, but it's been harder to explain why he seems like such a rarity. "I'll tell you where you find him," said Kansas City QB coach Jim Zorn. "Look at the league. He's playing defense."
In talking to evaluators here, the consensus is what you might suspect, and it's not some deep dive into economics and laws of scarcity -- it's pretty basic: Over the past two-plus decades, the sophistication of passing offenses has grown while the rules dictating how to stop them have become harder to follow, and it goes well down into the early high school levels (just look at the 7-on-7 explosion).
The shorter, lighter, quick-twitch athletes like Sproles are being pushed onto defense, to help cover the 53.5-yard width of the field that offenses are better at exploiting. The traits of a great space player such as Sproles -- upfield burst, if not always a galloper's straight-line speed (Sproles ran a 4.49 40 at the combine), lateral quickness, explosive change of direction, fluidity in and out of breaks -- are most valued in corners, which is why so many have also specialized in the return game (see: Deion Sanders, Patrick Peterson, Devin Hester) as Sproles does.
It's also a part of the reason guys like Sproles are back en vogue on offense:
• For one, in the zeal to counter offenses that can create space and use the full width of the field with greater passing chemistry, if not the overstated "sophistication," defensive speed and range is as valuable as ever. Spread-out defenses are susceptible to space players, even more so than lumbering backs. Sproles averaged a startling 10.62 yards per carry on third down last season, as nickel and dime defenses tried to defend the Saints. And he was also used a lot inside, often on draws. Linebackers would know he had the ball but, like tracking a rabbit fleeing a darkened tree line, were often even with Sproles before they could react to seeing him. (Sproles isn't alone. Reggie Bush had good success running inside with Miami this season, just as Jamaal Charles did in 2010 in Kansas City.)
• Secondly, the idea of a Sproles-type as some kind of fragile, gadget-only weapon is fading. That's because all backs are seen as fragile. Size isn't the great indicator of fragility at running back, the term "running back" is. Of the highest one-season carry totals of the past decade, just two came in the past two years, and neither was very high. Maurice Jones-Drew led the NFL in carries in 2011, but that total was just 23rd highest this decade. Sean Payton drafted Mark Ingram, considered more of an every-down RB, in the first round last year, and gave him just 122 carries in 10 games because, as Payton says, he doesn't really buy the notion of an every-down back. The limitation here is blocking and blitz pick-up, but part of the appeal of the smaller back is as a dump-off threat against blitzes. His presence can limit them, in some cases.
• Lastly, the medical side agrees "smaller" isn't necessarily "susceptible." In talking to people on that side, you hear that it's not who is hitting you, it's how you are taking hits. Few tacklers can get low on Sproles, and he often bounces off of contact -- direct hits are rare -- or he finishes runs with a dive for extra yards. Marvin Harrison made a career of using his small size to avoid hits; Sproles hasn't missed a game in four years.
Over the past 25 years of the NFL draft, just five running backs safely under 200 pounds have been drafted in Round 1. Gaston Green (1988) and Warrick Dunn (1997) were the only two taken in a 22-year period.
But in the past three drafts, we've seen Chris Johnson, C.J. Spiller and Jahvid Best taken in Round 1 as guys built for space, and Dexter McCluster was drafted early in Round 2 in 2010 as a fit to the Sproles profile. The results have varied -- Johnson was brilliant but overused, Best has been very good when healthy, Spiller is emerging -- but the trend is obvious.
"It's not a secret teams are looking hard at these guys," said colleague Mel Kiper. "Even as decoys, they create problems for defenses."
Sproles wasn't taken until the fourth round in 2005. If someone gets the "Sproles" comparison this year, he won't last quite as long.
Here are some guys to look at in the 2012 draft:
Chris Rainey: Just 5-8, 180, Rainey passes the Sproles size test, but he's also similarly fast, running a 4.45 40, and it's track speed that evaluators say translates to the field. Rainey also is a really good route-runner out of the backfield, a skill Sproles had to develop. Rainey went 3.93 in the 20-yard shuttle, crushing the field, and broke the combine record in the three-cone.
LaMichael James: The Oregon star is 5-8, 194, and at one time carried a first-round grade. He reaches full speed quickly -- that's good when you're also able to run the 100-yard dash in 10.76 seconds -- and has never been shy about running between the tackles.
Devon Wylie: Listed as a receiver, Wylie is 5-9, 187, but can fly -- he ran a 4.39 40 -- and could become a star return man for whoever gets him. He could be had in the fourth round and provide big plays early in his career.
Isaiah Pead: He's a little on the heavy side, having bulked up to 197 pounds, but Pead shouldn't get bigger and sacrifice explosiveness, following a guy like Charles, who was a 10.23-second 100-meter sprinter at Texas and played at around 190 pounds. Pead is really explosive to the edge and could be a home run hitter in the NFL.
Rodney Stewart: More of a long shot, Stewart is just under 5-7, 176, but he holds the career record for carries and all-purpose yards at Colorado, which says he might have Sproles' "bounce" skills when it comes to tacklers. His offensive coordinator at Colorado, by the way, is the 5-7 Eric Bieniemy, who played nine NFL seasons as an "undersized" guy.
Chris Sprow is a senior editor for ESPN Insider. He reports and edits on many sports and works year-round with Mel Kiper on NFL draft coverage. He also oversees ESPN's Rumor Central and has been a regular guest on ESPN networks in that role. You can find his ESPN archives here and find him on Twitter here.