When Adrian Peterson is healthy, he’s the best running back in the NFL.

But he’s not healthy.

Adrian Peterson has a rare combination of strength and speed, and can both bowl you over and juke you to the ground.

But he tore his ACL in the final game last year, and at this point you’re not sure if he can be trusted to carry your groceries up a set of stairs, let alone anchor your fantasy backfield.

Adrian Peterson says he’s fine, though, and he’s been back at practice and working out in full pads for over a week now without a setback of any kind.

But he won’t play in a pre-season game, meaning his first game action since tearing apart his knee will come in an environment with the intensity heightened, and the opposition more motivated to see if he really has healed.

This is the kind of internal battle happening right now wherever fantasy draft prep is taking place, whether it’s a kitchen table, on public transit, or a treehouse. There’s optimism growing quickly around Peterson, even if the “buts” are still making a strong case. To a lesser extent the same discussion surrounds Jamaal Charles, but the Chiefs running back has quieted concerns by participating in both of his team’s pre-season games, and taking hits directly to his own injured knee.

The difference, however, is that Charles tore his ACL way back in Week 2 of last year, giving him a three-month head start in his recovery before the 2011 season even ended. Peterson, meanwhile, waited until the regular-season finale to do his own shredding, leaving potential fantasy owners to wait, hope, and maybe eventually guess.

So what should you do with Peterson? Nothing, because at the position where he’s currently being drafted, there’s nothing you can do. Just have faith, and hope history repeats itself (in a good way).

I’ll preface this with the standard disclaimer that every NFL body is different, and previous case studies don’t directly connect to future recoveries. However, when we look back on running backs who’ve suffered ACL tears over the past decade or so, the sample size may be small, but we see numbers that either didn’t decline, or they declined only marginally.

Edgerrin James is a commonly-used example of ACL recovery failure. We won’t use that word here, partly because I’m still doing some recovery of my own following the mental anguish of owning him for the 2002 season. James played only six games in 2001 before tearing his ACL, and over the previous two seasons before the injury he had accumulated 4,442 yards from scrimmage, with 35 touchdowns. So sure, that made his 1,343 yards from scrimmage in 2002 (989 on the ground) with only three TDs disappointing, and the kind of disappointment that sends heads to toilets.

That’s the cautious ACL tale, and caution is certainly something you should use while handling Peterson to ensure that you don’t foolishly overpay. But consider this: right now with 19 days left before the Vikings begin their regular season, Peterson is coming off the board at the 21st position in ESPN leagues. That’s late in the second round in 12-team leagues, and he’d be the first pick in the third round in 10-team leagues.

Feels a little dangerous, doesn’t it? But look at the other running backs surrounding Peterson at that position. Darren McFadden (22.2) is arguably an even greater injury scare than Peterson after he’s missed 19 games over his four-year career. Put in another more haunting way, McFadden’s missed almost 30 percent of the games he’s been eligible to play in (29.7 percent).

Sure, you could move DeMarco Murray ahead of Peterson (22.3 ADP), but if trust is your issue, he’s only logged seven career starts, and he also missed the final three games last year. Then there’s the aforementioned Charles with his own more promising but still concerning injury (24.5), followed by a tumble down to the next tier and the aging Steven Jackson (31.0).

This started as an exercise to explore the draft strategy around Peterson (and it still is), but now it’s also become an illustration of why beyond the top four of Arian Foster, Ray Rice, LeSean McCoy, and Maurice Jones-Drew once he inevitably reports to Jacksonville, there’s danger lurking everywhere among just the second tier of RBs. So even though he suffered a late-season ACL injury and could be slowed for the first few games, Peterson is one of the safest options amongst a muddled middle filled with danger.

But hey, buck up, because we haven’t even mentioned the encouraging examples of ACL recovery. In 2001 Jamal Lewis did his ACL rippage, and then he rushed for 1,327 yards the next year, adding 442 more yards through the air. Then there’s Ronnie Brown, who had his rip in 2007, and then had 916 rushing yards in 2008, his second best rushing season.

So there’s history on Peterson’s side, and that’s swell, because here’s a particularly frightening hypothetical. You’re in a 10-team league with the second overall pick, and you opted for an elite QB early instead one of the top running backs (let’s say Aaron Rodgers). It’s a snake draft, and it’s now swung back to you at the end of the second round. Passing on an RB again isn’t an option, so you’re picking from the scary group mentioned above.

Do you go with Murray’s upside to minimize risk, or trust that Peterson will be fine? It’s not hard to justify the Murray pick, and while there’s risk with Peterson, paying a late second-round price for his elite production when fully healthy is still a manageable gamble.

Beyond those two, it’s a forest of injury risks and time shares.