Even casual NFL fans know that the running back position has been devalued in recent years. For the most part, gone are the days of the feature workhorse back. Instead, teams are opting more for a collection of ball carriers with varied skill sets. Teams no longer invest significant resources in the position. No running back has been taken in the first round of the draft since 2012 and Chris Johnson, the top free agent RB last offseason, signed for just two years and $8 million before being released this month.

But that could all change once free agency opens next month. This year's free agent running back class has the chance to feature some of the best ball carriers in the game. So, who are the top options that could potentially become available this offseason?

1. Marshawn Lynch

Lynch is reportedly mulling retirement, unhappy with his current contract and a host of other thoughts that the media is not privy to. The Seattle Seahawks have made it known that they want Lynch back in 2015. But if he does decide to return, there is no guarantee he and Seattle will be able to work out a new contract. Remember, it wasn't that long ago that all rumors coming out of Seattle were that Lynch's time with the team was limited.

Since joining the Seahawks in 2010, Lynch leads all running backs in carries, rushing yards and rushing touchdowns. Despite his immense workload, Lynch has not missed a game since 2011. Beast Mode would be a welcomed addition to any running back-needy teams such as the Arizona Cardinals or Indianapolis Colts. However, the most likely scenario is that he ends up back in Seattle.

2. Adrian Peterson

Normally, All Day would top any rankings list when it came to running backs, but Peterson will turn 30 next month and missed all but one game last season. Of course, he isn't your typical ball carrier. This is the same guy who ran for over 2,000 yards when he returned from a torn ACL. But at this point, he's more of a question mark than a certainty.

The Minnesota Vikings have expressed interest in retaining Peterson, but it is highly doubtful that the team will want to pay his $15.4 million salary cap hit. If the two sides can't agree on a restructuring, Peterson could hit the open market.

3. DeMarco Murray

Murray is younger (27 years old) than the two names above him on this list. He's also coming off the best season of his career in which he led the NFL with 1,845 rushing yards and added 13 touchdowns and 57 receptions to boot. Not a bad stat line to put up in a walk year.

But Murray also has a history of injuries, missing 11 games in his first three seasons and suffering a broken bone in his hand this year. Add in his almost 450 total touches from 2014 and teams might think twice before handing him a mega deal in free agency.

4. Ryan Mathews

Mathews is another talented running back who has been rightfully labeled as injury-prone. The 2010 first-rounder has played in all 16 games just once his career, missing 10 games last season due to several knee and ankle sprains.

When healthy, Mathews has proved to be a solid dual-threat option. He's topped 1,000 rushing yards twice in his career while also catching at least 22 passes in all but one season. He will meet with San Diego brass this week, but it wouldn't be a surprise to see him on a new team next season.

5. Mark Ingram

It took four years, but Ingram finally broke out this past season. The former first-round pick was never a great fit in the pass-happy offense of the New Orleans Saints. But this season, with increased usage, Ingram proved why he was once a first-round talent. The former Alabama star set career highs in carries (226), rushing yards (964), touchdowns (9), receptions (29) and receiving yards (145).

Ingram did miss three games this past year due to injury, but his midseason stretch of dominance should be enough to entice a team to pony up in free agency. With New Orleans expected to be over the cap, it's possible that Ingram could be wearing a new uniform next season.