Jamaal Charles is now a Denver Bronco, making him the second superstar running back in two weeks to join a new team at the tail end of his career. In his prime, Charles was a very good receiver and a player that could be the centerpiece of an offense. However, he will likely be remembered for a singular skill: rushing efficiency.

Charles has a career YPC average of 5.45, easily the best in history among running backs in the NFL. That number is at least a little misleading. While rushing efficiency has not soared the way passing efficiency has, we are currently in a high-YPC environment. Two years ago, I calculated era-adjusted yards per carry: at the time, Charles was at 5.49, while the league average was 4.21. For reference, the league average during the careers of Jim Brown, Gale Sayers, and Barry Sanders was 4.08, 3.95, and 3.93, respectively.

I am not a big fan of yards per carry as a statistic, but hey, it’s still interesting trivia. It’s a little silly and mostly an academic exercise, but let’s pretend that we replaced every Charles rush attempt with a league average rush attempt. How much worse off would Kansas City have been? Well, a whole lot. Let’s use his 2010 season as an example. He had 230 carries for 1,467 yards, producing an incredible 6.38 YPC average. The league average that season was 4.21, meaning he was 2.17 YPC above-average. Given his 230 carries, we would have expected him to rush for just 968 yards, meaning he produced 499 rushing yards above average. And for his career? Charles is at +1657.

Year Rush Yds YPC LgAvg YPC Diff Exp RushYd Diff 2008 67 357 5.33 4.20 1.12 282 75 2009 190 1120 5.89 4.24 1.65 806 314 2010 230 1467 6.38 4.21 2.17 968 499 2011 12 83 6.92 4.29 2.62 52 31 2012 285 1509 5.29 4.26 1.03 1215 294 2013 259 1287 4.97 4.17 0.80 1079 208 2014 206 1033 5.01 4.16 0.85 858 175 2015 71 364 5.13 4.13 1.00 293 71 2016 12 40 3.33 4.19 -0.85 50 -10 Total 1332 7260 5.45 4.21 1.24 5603 1657

I calculated this for all running backs in NFL history. As it turns out, Charles ranks 4th in rushing yards above (YPC-based) expectation:

Charles also ranks “only” 3rd in YPC differential, behind 1930s superstar Ernie Caddel and AAFC superstar Marion Motley. Now in Denver, it seems unlikely that Charles will increase his career YPC average, although he will only need gain yards at an above-average clip to move up the raw differential list. He’s currently 179 yards behind Joe Perry, which means he needs one more season on par with what he did in 2014, or a few less-impressive above-average years.