You knew it was coming. The writing was on the wall that Adrian Peterson's time with the Minnesota Vikings would soon end, and it all became official on Tuesday.

Coming off of an injury-riddled and ineffective season, Peterson will hit the open market once free agency begins on March 9th. This is going to be interesting.

Peterson is entering his age-32 season -- well past the sweet spot for a running back -- and he has exceeded 40 carries just once in the past three seasons. We know what he can do when he's fully healthy, but 2016 also showed that this guy is far from being the beast he once was.

What does this mean for Peterson in free agency? Let's try to break this down with the help of numberFire's Net Expected Points (NEP), the metric we use to track the efficiency of both teams and players. NEP helps quantify the difference between a 2-yard carry on 3rd and 1 and a 2-yard carry on 1st and 10 to better illustrate the effectiveness of a running back. For Peterson, we'll be focusing on Rushing NEP per carry -- the expected points he adds or subtracts on a per-carry basis -- and Success Rate, which shows the percentage of plays on which he increases the team's expected points for the drive.

We know Peterson will garner interest in the open market, but based on what NEP has to say, teams may be better suited focusing their efforts elsewhere.

A Nightmare 2016 Season

If you're making a pitch for a team to sign Peterson, you may want to gloss over the 2016 file. Things got ugly fast.

Just two games into the season, Peterson suffered a torn meniscus in his knee, forcing him to undergo surgery. He didn't play again until Week 15, and after just six additional carries, his season was done.

This gives us only a 37-carry sample to check out for Peterson, but it says an awful lot. Peterson's 37 carries resulted in -14.42 Rushing NEP for the Vikings, meaning they lost an average of over one third of a point each time he touched the football. If he had gotten zero carries, the team would have scored an expected two additional touchdowns over the course of the year. Woof.

Sure, part of this was a costly fumble in Week 15, but it was far more than that. Only 9 of his 37 carries increased the team's expected points for the drive, a 24.32% Success Rate. Here are his NEP metrics compared to those of a league-average back for the year.

numberFire's databases go back to the 2000 season, since which there have been 1,331 individual running-back seasons of at least 35 carries. Of them, Peterson's 2016 ranks 1,329th in Rushing NEP per carry and 1,320th in Success Rate. It was one of the worst seasons for a running back this century.

Now, comparing Peterson's metrics overall may not exactly be fair given the surrounding situation he had in Minnesota. It's well documented that the Vikings' offensive line was a billowing dumpster fire from jump street, something that would obviously have an adverse effect on his numbers. But even when we compare him to Matt Asiata and Jerick McKinnon in that same environment, Peterson comes up short.

Here are their NEP metrics from the season side by side. Even though the entire team was below average, it's clear which guy lagged behind.

The offensive line was certainly part of Peterson's struggles, but it can't nearly explain all of it. What makes it even more damning is that Peterson's first two games came when the offensive line was at peak health. Starting tackles Matt Kalil and Andre Smith both played every snap in those two games before later hitting injured reserve. If anything, Peterson's offensive line may have been better than what McKinnon and Asiata got to run behind, further tainting his already-vomit-worthy efficiency.

With all of this said, it is still important to remember that this was just a 37-carry sample and Peterson dealt with injuries while playing in a poor situation. That may make it more worthwhile to go back to 2015 when Peterson led the league in rushing, but even then, we see causes for concern.

A One-Dimensional Offering

Obviously, if Peterson led the league in rushing in 2015, something was going right. And that's completely true. But it wasn't really enough to inspire enthusiasm a full two years down the road.

Of the 44 running backs with at least 100 carries, Peterson finished 12th in Rushing NEP per carry and 23rd in Success Rate. His Success Rate was beneath guys like Jeremy Hill, Charcandrick West, Doug Martin, and Justin Forsett who have since had troubles holding down starting jobs. Peterson wasn't bad, but he also was more dependent on volume than you would ideally hope.

If Peterson offered anything in the receiving game, then his efficiency would be less of a concern. As you know, though, that's not part of Peterson's repertoire. He finished the 2015 campaign with just 36 targets, tying him for 38th most among all running backs. The Vikings gained just 2.33 NEP when targeting Peterson, as well, meaning he wasn't particularly effective when they did give him looks. You know what Peterson is, and it's unlikely he'll be diversifying his skillset as he enters the tail end of his career.

This means that Peterson -- in his current state -- is a one-dimensional back whose most recent volume was horribly inefficient. Sure, he could still rekindle that magic he had early in his career, but is that the most likely outcome for a player who will turn 32 in March?

A Risky Proposition

As a former MVP, Peterson is going to garner interest from prospective teams. And as long as teams view him for what he currently is, that's completely acceptable. But it doesn't lower the risk of his current profile.

Our most recent exposure to Peterson was at horrifying efficiency that was lesser than his teammates who were in similar conditions. He was fine back in 2015, but he's now two years removed from that and already beyond the prime years for his position.

Peterson was a tremendous runner in the past, but he was only that: a runner. He has never been a player heavily involved in the passing game, putting a cap on his value in today's NFL. If we don't know that he can still be that runner -- which is very much in doubt after last year -- it would seem a stretch to say he's still a desirable asset for a 2017 roster.

Peterson will likely be remembered as one of the best running backs of all time, and his resume shows that he has earned that reputation. But past results can't predict future output, and teams would be wise to disregard his former production and view Peterson as the risky investment he truly is.