Is this the smiling face of a man who can account for 40 percent of a team's offense?

Of all the finely-tuned athletic machines on NFL rosters, the ones most vulnerable to the quick onset of rust and decay are the running backs, a position that can often present unmatched physical tools during the draft that are too intriguing for a general manager to resist.

We hear this same word of caution every year in mid-February and early March as the draft buzz begins to build, and football bloggers start to assemble their early mock drafts filled with predictions they’ll regret in 12 months. But rarely are those fears quantified by someone who’s actually drafted an NFL player, and managed an NFL team.

That’s the one benefit we’ve now received after the Colts fired Bill Polian, the long-time executive who logged 15 years in the Indianapolis front office before his dismissal earlier this offseason. Needing something to occupy his time that involved football, but not Jim Irsay, Polian took a gig as an analyst for NFL Radio.

During a guest appearance yesterday on Mad Dog Radio, another Sirius/XM channel, Polian was asked about his approach to drafting running backs in the first round. After reciting the usual warning about both the brittleness and depth at the position that often make drafting a running back early risky and often senseless, Polian provided his measuring tool, saying that for a team to justify a first-round pick on a running back–and especially an early pick in the top 15–they have to be confident that the player will account for 40 percent of their offense in the very near future. That number stems from an elite running back’s ability to be versatile, and compile both receiving and rushing yardage.

Polian drafted three running backs in the first round throughout his tenure in Indianapolis, and only one was among that elite group, and deemed worthy of a high pick at the very top of the draft. Edgerrin James was taken fourth overall in 1999, while both Donald Brown and Joseph Addai nearly fell into the second round (Addai was 30th in 2006, and Brown was 27th in 2009).

James is the only pick of those three to even come close to Polian’s mark, and his 2000 season when he rushed for a career-high 1,709 and added 594 more through the air shows just how difficult it is to crack the 40 percent plateau. James fell just short that year while the Peyton Manning to Marvin Harrison connection was in its prime, accounting for 37.5 percent of Indy’s offense. He also came close the previous year (37.4), but the highest total over his other five years in Indy was 31.9.

If reaching or at least approaching 40 percent is indeed the proper standard for an elite running back worthy of a lofty draft investment, then this year’s top ten rushers also showed how difficult it is to represent nearly half of your team’s offense.

As shown below, Maurice Jones-Drew was the only back in the top 10 to reach and exceed Polian’s standard. Ray Rice also came close, but along with┬áJones-Drew and Michael Turner he was one of just three to account for at least 35 percent.

  • Maurice Jones-Drew: 47.7 percent (1,980 yards from scrimmage)
  • Ray Rice: 38.7 (2,068)
  • Michael Turner: 36.0 (1,508)
  • LeSean McCoy: 25.4 (1,624)
  • Arian Foster: 30.9 (1,841)
  • Frank Gore: 26.6 (1,325)
  • Marshawn Lynch: 34.9 (1,416)
  • Willis McGahee: 24.7 (1,250)
  • Steven Jackson: 32.6 (1,478)
  • Ryan Mathews: 24.6 (1,546)

Four of those names were drafted in the first round (Lynch, McGahee, Jackson, and Mathews). But more importantly, only two were taken in the top 15 (Mathews and Lynch), and none in the top 10.

Combined those 10 running backs missed nine games this year, meaning they were all relatively healthy, but still exposed to the constant pounding demanded of their position. That’s part of Polian’s equation in his math that led to a 40 percent contribution being ideal, and the other half is the offensive scheme.

Even if every key Texans player was healthy for the full season including Foster, he likely still wouldn’t reach 40 percent with Andre Johnson commanding attention in Houston’s passing offense. The same can be said for Turner, who’s in the same huddle as Julio Jones and Roddy White.

And that’s the underlying message here from Polian. If you’re not confident in a running back’s durability, and you’re not confident enough in his talent to make him the center of your offense, then you’re also not confident enough to draft him.

Trent Richardson will likely come off the board within the first 10 picks this April, and Mel Kiper has him going to the Bucs at No. 5 in his latest mock draft. Meanwhile, Mike Freeman of CBS Sports wrote earlier today that if they don’t re-sign Peyton Hillis, the Browns are considering the Alabama RB one spot earlier, even though Robert Griffin III is a much smarter pick.

Richardson is the only running back widely projected for the first round, and GMs now have just over two months to assess both his health, and his ability to carry an offense for the next decade.