Who is having the best rookie season from a crowded NFL running back class?

When Melvin Gordon injured his knee early in the third quarter of the Chargers’ blowout win over Arizona on Sunday, college football fans got to enjoy an “Oh right, that guy!” experience.

Gordon is expected back by the postseason, which is excellent news for what might be the most well-rounded team in the NFL. But in the meantime, it appears rookie Justin Jackson will get a few more reps. You know, that guy from Northwestern, the one with four 1,000-yard seasons in Evanston, the guy who rushed for 224 yards against Pitt in a bowl a couple of years ago.

Jackson ended up rushing seven times for 57 yards against the Cardinals, including a 19-yarder that set up a touchdown and a 20-yarder that set up a field goal.

Jackson is one of quite a few rookie backs who have been tossed into the deep end of the pool this year. At a time in which both the value and proper use of running backs is coming into question more than ever, eight backs were selected in the first 71 picks of the 2018 NFL draft, and 12 have been given at least 50 intended touches (rushes plus pass targets) this year.

Though Jackson’s moment was not quite a moment, quite a few of these rookies have had breakout moments this season.

That last part is key. It’s why I framed guys’ stats in terms of intended touches below. We’ve understood for a while that the concept of the old-school, 25-carries-a-game running back has become rather outdated; running backs are viewed as far more interchangeable than they used to be, and there’s data to back up that notion.

But whatever a “marquee back” is going to become in the coming years, it’s probably going to look like Barkley. The Penn State product is indeed averaging 15.5 carries per game, but he’s also been targeted by 7.9 passes per game. He’s on pace for both 1,200 rushing yards and 850 receiving yards.

While Barkley’s easily the standard bearer for the “Roger Craig of the 21st century” role, other rookies have at times proven their worth in the passing game — Nyheim Hines, a former slot receiver at NC State, has 40 catches to go with his 69 carries, while Johnson (32 catches), Lindsay (24), and Ito Smith (21) have all contributed in this regard. It’s the pathway to avoiding interchangeability.

But let’s go back to talking only about rushing for a moment.

During the run-up to the draft, I wrote about the relationship between a back’s college and pro stats and how one translated to the other.

The thesis of my recent quarterback draft analysis piece was that while stats can’t necessarily tell you how a player will perform, they can define that player’s ceiling. And just as quarterbacks aren’t going to exceed their college efficiency values, neither are running backs.

Sixty-six halfbacks were drafted between 2010-17 and carried at least 75 times in their rookie seasons. Only about seven came close to matching their college marginal efficiency.

Only nine of the 66 in this sample came within 3 percentage points of their college efficiency level. So if you’re inefficient in college, that’s not going to change, no matter the line in front of you, the quality of opposition, etc.

(As a quick reminder, marginal stats take my go-to measures — success rate for efficiency, Isolated Points Per Play for explosiveness — and adjust for expected values based on down, distance, and field position. You can read more about the concept here.)

How has that trend held up with the rookie class so far? Here are the marginal stats for each of the 11 rookie backs to have carried at least 50 times this year:

Obviously it’s early in these players’ respective careers, but thus far the “your college averages are your professional ceiling” concept rings very much true here, with one particular exception.

Among the backs listed above, Lindsay had the second-worst college marginal efficiency (ahead of only Hines) and the second-worst marginal explosiveness (ahead of only Johnson). He spent his last two seasons at Colorado as a high-volume, middling-output back, putting together occasional huge outbursts (60 carries for 421 yards against Colorado State and Arizona his senior year) with long strings of mediocrity (4.4 yards per carry in the other 10 games of his senior year).

Thus far with the Broncos, though, he’s been the revelation that Royce Freeman was supposed to be. He has produced at least 100 combined rushing and receiving yards in five games, including three of the last four; not only that, but the Broncos are 4-1 when he does so, with the only loss a one-score defeat at the hands of the 9-2 Chiefs. (For those keeping score at home, that means the Broncos are 1-5 when he doesn’t hit that combined century mark.)

Lindsay hasn’t done much from an explosiveness perspective, but his hard-charging style makes the most of his slight frame (he’s listed at 5’8, 190), and he is really hard to bring down before he’s gained at least three or four yards. He has thus far proved that you can potentially exceed your college stats ... at least, if your college stats are pretty mediocre.

There are two potential reasons for this exceeding of statistical boundaries:

Regardless of Lindsay’s potential regression, though, marginal stats do seem to remain an effective way of gauging your pro ceiling. The floor, however, is less certain. And you can make quite a bit of money by figuring out how to carve out a niche closer to the former than the latter.