The preseason position rankings march on with the running back units in the Big Ten. If you missed the top 10 individual running backs entering 2012, check them out here. For the running back units -- and all position units, for that matter -- the strength of the starter is weighted fairly heavily. But if a team has a good starter and no proven depth behind him, it could hurt the rating a bit.

The top team here is obvious, while the next four groups all are very good. There's a bit of a drop off after No. 5. Several squads have virtually no depth, which is why they're at the bottom.

Let's get to it.

1. Wisconsin: The obvious choice for the top spot as Wisconsin returns two backs who would start for most FBS teams. Heisman Trophy finalist Montee Ball is back following a record-setting season, and James White has rushed for 1,765 yards and 20 touchdowns in his first two seasons. Wisconsin also has a future star behind them in Melvin Gordon.

2. Nebraska: Although Aaron Green's transfer to TCU hurts Nebraska's depth, the Huskers still boast a strong 1-2 punch in Rex Burkhead and Ameer Abdullah. Abdullah has had a strong offseason and should be able to spell Burkhead more this fall. Freshman Imani Cross is a good get on the recruiting trail.

3. Michigan: Running back could be Michigan's deepest position entering 2012 as all the key names come back. Fitzgerald Toussaint established himself as the featured back during Big Ten play, and he'll be backed up by versatile senior Vincent Smith and Thomas Rawls, who appeared in 10 games as a freshman last year.

4. Michigan State: Like Nebraska, Michigan State loses a key running back in Edwin Baker, who surprised some by entering the draft a year early. The Spartans still boast a potential star in Le'Veon Bell, along with veteran Larry Caper, a former starter, and the speedy Nick Hill.

5. Penn State: What the Lions lack at quarterback and wide receiver, they make up for at running back. Silas Redd returns for his second season as the starter, and Penn State has some insurance behind him with players like Curtis Dukes and Bill Belton, who moves over from receiver.

6. Ohio State: A healthy Jordan Hall makes this a much stronger group, as the senior can fill the hybrid role (tailback/receiver) in Urban Meyer's offense. Hall's absence early in the season will place a heavier burden on Carlos Hyde, who looked good at times last season. Freshman Bri'onte Dunn and sophomore Rod Smith are in the mix, but there's no obvious star here.

7. Purdue: The Boilers have some nice options at running back, and they'll be even better here if former All-Big Ten selection Ralph Bolden returns at or near full strength. Co-captain Akeem Shavers enters the fall as the lead back, and he'll be complemented by speedy sophomore Akeem Hunt.

8. Indiana: Although IU will pass the ball more in 2012, it has several options in the backfield alongside quarterback Tre Roberson. Stephen Houston emerged as a reliable option in Big Ten play last fall. He'll be the lead ball-carrier, but Morehead State transfer Isaiah Roundtree will push for carries after a strong performance this spring. D'Angelo Roberts and Matt Perez also should help if they can stay healthy.

9. Illinois: New coach Tim Beckman is concerned about the lack of depth here, but he could have two good options in Donovonn Young and Josh Ferguson. Young got his feet wet as a freshman and rushed for 451 yards and six touchdowns, while Ferguson sparkled during the spring game and should be a valuable asset if he can stay healthy. The big question is who else emerges in the backfield.

10. Northwestern: The Wildcats are by no means loaded at running back, but they have fewer depth questions than the other two teams on the list. Mike Trumpy, who has looked like the team's best back when healthy, returns from a knee injury and likely will enter the fall as the starter. Treyvon Green also returns, Venric Mark moves over from receiver and incoming freshman Malin Jones will play a role right away.

11. Iowa: If the Hawkeyes had Marcus Coker and a healthy Jordan Canzeri, they'd be in the top six. Unfortunately, Iowa has neither player available right now, leaving a group of unproven players. The good news is Iowa always finds someone to carry the ball, and one of its two incoming freshmen -- Greg Garmon or Barkley Hill -- could be the next in line. If not, Iowa will need Damon Bullock or De'Andre Johnson to make major strides.

12. Minnesota: Like Iowa, Minnesota is banking more on potential than anything else. Junior college transfer James Gillum could be the answer to the Gophers' sputtering ground game. Perhaps Donnell Kirkwood can stay healthy or become a difference maker. But when Kirkwood (63 carries last year) is the top returning rusher outside of quarterback MarQueis Gray, there's reason to be concerned.