If you had to use one word to describe Alvin Kamara's rookie season, you might go with freakish. Or maybe you'd call it extraordinary.

Me? I'd say it was unsustainable.

Kamara was the most effective running back in the NFL last year, according to numberFire's expected points model, and he did things that we really have never seen before.

Do you know how many running backs in NFL history have averaged more than 6.0 yards per carry while toting the rock 100-plus times during their rookie season? There's been one, and his name is Alvin Kamara. Do you know the number of backs who've been able to average at least 6.0 yards per attempt and 10.0 yards per reception while running the ball 100 or more times in any season? Five. There've been five. In NFL history. And one of those five is Alvin freaking Kamara.

There's a reason so few running backs have done what Kamara did during his first year in the NFL -- it's really hard to do it. And, as a result, Kamara's going to see what nerds call regression, or a return to a former or less developed state.

Kamara is bound to be less efficient this season.

But that doesn't mean he's going to be overrated in fantasy football. In fact, Kamara can easily still finish as a top-five running back this year.

Unsustainable Production

"Maybe Alvin Kamara is just different."

Maybe. But probably not.

No running back has had multiple NFL seasons with 100 or more carries and a yards per carry rate north of 6.0. Sure, no runner aside from Kamara has done that as a rookie, but we have to recognize that Kamara would have to be historically good to produce like he did in 2017 ever again. And when projecting a player's most likely outcome for the upcoming season, you can't work off of an assumption that said player is an outlier. I mean, you can, but that's not going to give you consistently good results.

Kamara's yards per carry rate isn't the only thing that was bonkers last year. He also scored at an incredibly high rate, finding the end zone 13 times on 201 total touches (120 rushes and 81 receptions). For some context, over the last five seasons (and Kamara aside), the fewest number of touches seen by a running back who also scored 13 or more times was 246, set by Jamaal Charles in 2014 (246 total touches, 14 touchdowns).

Here's a glimpse of how successful Kamara was at finding the end zone versus the league's average by a running back over the last five seasons:

Had Kamara scored a rushing touchdown at the league average rate of 35.75 attempts per touchdown, he would've had nearly 5 fewer rushing touchdowns last year. And had he scored at the receptions per receiving touchdown rate, we're looking at almost two fewer receiving scores. That's a change from 13 touchdowns scored down to 6, which would've made him last year's PPR RB7 instead of the league's RB3.

So not only are we looking at a probable decrease in yards per carry, but Kamara more than likely won't be scoring at as high of a rate in 2018, as well.

That's no problem, fantasy owners.

A Change In Usage

Volume is everything in fantasy football, which is really what makes Kamara's 2017 all the more obnoxious. He did what he did without the most important aspect of the game.

Understanding the balance of volume and efficiency is vital when projecting a player's output. Basic logic tells us that a running back with 200 carries and 10 targets is more valuable than one with 100 carries and 5 targets, but if the latter player is twice as efficient at creating yards, then the volume side of the equation matters a whole lot less.

If Kamara sees more volume, it can combat the impending regression.

It seems reasonable to think he'll see more touches in 2018. Last year, Kamara averaged fewer than eight carries per game and was drastically out-touched by teammate Mark Ingram on the ground.

The thing is, these numbers are distorted a bit by what happened at the beginning of the season. Kamara carried the ball a grand total of 15 times across the first four games of the year -- four games that the Saints had Adrian Peterson. That means he had 105 attempts during his final 12 games. One of those games featured a single carry due to an early-game concussion, so we're actually looking at 104 attempts across 11 games, or 9.45 carries per contest.

Here's how the same breakdown looks in those 11 contests:

Both running backs saw an uptick in attempts per game and overall rushing share (the percentage of rushes a player sees in his backfield) without Peterson in the mix last year. Had Kamara seen that 31% rushing share across all of last season, his total attempts would've been closer to 138 instead of the 120 that he finished the season with.

A 31% share isn't anything to write home about, though. That was met by 35 different running backs last season, after all.

But shouldn't we assume he'll see some growth in that department as a sophomore in the league?

It's true that the Saints generally don't give a running back a large chunk of the team's attempts. During the Sean Payton era, the largest rushing share seen by a player in a New Orleans backfield has been about 56%. That's barely a top-10 number in any given season across the league.

On top of this, Kamara hasn't shown he's a workhorse back. That's not just based on last season -- Kamara's biggest red flag coming out of college was his lack of volume, having run the ball only 210 times across two seasons at Tennessee.

So where does that put us?

Well, the initial potential rushing share range for Kamara in 2018 appears to be from 31% (last year's non-Peterson share) to 56% (the maximum in the Sean Payton era). Ingram exists in the backfield, though, and despite his four-game suspension for performance enhancing drugs, he'll still be involved.

Ingram's seen at least 42% of New Orleans' rushes in five of his last six seasons. If we see that as his low-end projection for 2018, then with a four-game suspension, we're looking at roughly 32% of the Saints' carries. Assuming the Saints keep a similar ratio between Kamara and Ingram -- they had 83.33% of the team's rush attempts last year -- that would leave Kamara with a rushing share of a little over 51%.

Is that realistic? Perhaps as a ceiling. Remember, we're under the assumption here that Ingram will see one of his lowest rushing shares as a Saint, and that Kamara is capable of carrying a large workload. Even if Kamara is capable, do the Saints want to see that?

If we want to be reasonable, Kamara's rushing share will probably land somewhere in the middle, maybe around the 44% range. That would've led to 195 carries last season, a huge jump over the 120 carries that he saw.

But things should be a little different in New Orleans this year.

A Different New Orleans Offense

The Saints became a run-heavy team last year, at least by the standards of today's NFL.

Because of the team's low pass-to-rush attempt ratio, Drew Brees failed to reach 4,500 passing yards for the first time since 2009. Most everything else looked great statistically for Brees, though. He finished with the fifth-highest adjusted net yards per attempt of his career, and on a per-drop-back basis, only four quarterbacks were better, according to numberFire's Le'Veon Bell, Todd Gurley, David Johnson, and Ezekiel Elliott in my projections. Had Ingram not been suspended, the projections would've favored Saquon Barkley over Kamara.

It's clear that even with obvious regression, Kamara will still dominate in 2018.