Throughout the preseason, we’ll take a look at the best – and worst – the NFL has to offer, unit by unit. Look for a new set of rankings every few days.

I took everybody’s comments about my quarterback unit rankings into consideration and I’ve decided to re-think the way I rate each unit. With that said, everybody who wanted the starter’s role to be weighed more heavily, you win. You always do.

With each new positional unit that gets posted, I will clarify what formula was used in each ranking and what the criteria were for ranking that unit.

Criteria for the running backs:

The starters were weighed the heaviest at 60% since they will see the majority of the snaps. A back that can carry the ball 20-25 times for an offense and pound out 100+ yards on the ground is optimal.

The backups will count for 30% seeing as how more and more teams are relying on two and, in some cases, three backs during a given season.

The rest of the 10% goes to the wildcard of this group and a player that is often overlooked in the running back unit. No team can undervalue the fullback position, the hard worker who doesn’t have nice stats, rarely scores touchdowns and doesn’t have the name recognition that the tailbacks do.

THE TOP 10

1. San Diego Chargers
LaDainian Tomlinson, Lorenzo Neal, Michael Turner
LaDainian Tomlinson does it all and does it all extremely well. He has scored 80 touchdowns in his first five seasons and has rushed for at least 1,200 yards in each of those years. Tomlinson is an unbelievable athlete who is a fluid rusher, receiver and occasionally passes well too. Michael “The Burner” Turner is a great complement who averaged nearly six yards a carry last year. Lorenzo Neal is their Pro Bowl lead blocker who is aiming for his 10th consecutive season of leading the way for a 1,000-yard back.

2. Seattle Seahawks
Shaun Alexander, Mack Strong, Maurice Morris
Reigning league MVP Shaun Alexander rushed for nearly 1,900 yards last year and scored an NFL record 28 total touchdowns. Maurice Morris is smaller than Alexander, but has been in Mike Holmgren’s offensive system for four years now and could step right in to a starting roll if Alexander were to ever go down with an injury. Pro Bowl fullback Mack Strong is a throwback blocker who loves to put his helmet on linebackers, and he caught 22 passes last year.

3. Washington Redskins
Clinton Portis, Mike Sellers, Ladell Betts, Chris Cooley
The Redskins finished seventh in the league last year in rushing thanks in large part to Clinton Portis setting a Washington team record of 1,516 yards. He scored 11 touchdowns and added 30 receptions for 216 yards. Ladell Betts is a quality backup who may be pushed into the starting role if Portis doesn’t recover quickly from his separated shoulder, and even Rock Cartwright stepped up with a 100-yard rushing day against the Rams last season. Mike Sellers was a touchdown machine in ’05 and Chris Cooley can be used as an H-back or tight end.

4. New York Giants
Tiki Barber, Jim Finn, Brandon Jacobs
Tiki Barber is yet another running back who proved last year that ball carriers don’t always show signs of slowing down when they hit 30 years of age. Barber was unbelievable last season while rushing for a career-best 1,860 yards and nine touchdowns. Brandon Jacobs is the Giants’ short-yardage back, but could handle more duties if he proves he deserves more opportunities. Fullback Jim Finn is a solid veteran.

5. Kansas City Chiefs
Larry Johnson, Ronnie Cruz, Michael Bennett, Priest Holmes
Larry Johnson is the real deal. With a full season to show what he can do, he has a tremendous chance of being the NFL rushing leader and may break some single-season records while he’s at it. Here’s why the Chiefs fall, though, and it should be pretty obvious: nobody knows if Priest Holmes is ever suiting up again and KC lost fullback Tony Richardson to Minnesota in the offseason. Richardson was one of the best fullbacks in the league and with Ronnie Cruz being mostly a special teams guy thus far in his career; he’s got some big shoes to fill. The Chiefs dealt for Michael Bennett this summer to fill in the depth chart behind LJ, but c’mon…it’s Michael Bennett.

6. Atlanta Falcons
Warrick Dunn, Justin Griffith, T.J. Duckett, Jerious Norwood
Warrick Dunn showed the rest of the NFL that running backs could get better with age as he is flourishing in Atlanta. He has continuously gotten better statistically over the past three seasons and loves the zone blocking scheme run by the Falcons. T.J. Duckett is a bruiser, but his time could be running out in Atlanta as he struggled toward the end of last year in short-yardage situations. Rookie third-round pick Jerious Norwood could be a sleeper to spell Dunn this year and fullback Justin Griffith is vastly underrated as an all-purpose fullback.

7. Cincinnati Bengals
Rudi Johnson, Jeremi Johnson, Chris Perry
Rudi Johnson is a workhorse back who broke his own single-season franchise record for yards last year with 1,458. Chris Perry, a dangerous receiver out of the backfield, averaged 4.6-yards per carry last season when he got the chance and the Bengals have said they want to get him more involved in the offense this year. Jeremi Johnson signed a contract extension through 2011, which is a big indication that this fullback is considered one of the best young blockers in the league.

8. Arizona Cardinals
Edgerrin James, Marcel Shipp, James Hodgins
Edgerrin James’ production was often overlooked in an explosive Colts’ offense, but he’ll bring his tremendous vision, slashing running style and receiving skills to the desert heat. Marcel Shipp is dependable and will be a nice change-of-pace back for James this season. James Hodgins used to block for Marshall Faulk when he was with the Rams and his huge frame will benefit James immensely.

9. New Orleans Saints
Deuce McAllister, Mike Karney, Reggie Bush
This unit is scary more than anything as Heisman Trophy winner Reggie Bush joins Deuce McAllister and up-and-coming fullback Mike Karney in the Saints backfield. McAllister suffered a season-ending knee injury last year, but should bounce back and show the power and speed he had before his injury. Wind Mr. Heisman up and let him do his thing, as Bush should be exciting to watch this year, if nothing else.

10a. Tampa Bay Buccaneers
Cadillac Williams, Mike Alstott, Michael Pittman
As a rookie last year, Carnell “Cadillac” Williams became the first player in NFL history to rush for 100 or more yards in each of his first three games. He finished the season ranked sixth in the NFC with 1,178 rushing yards and was the Bucs’ first 1,000-yard rusher since Warrick Dunn ran for 1,133 yards in 2000. Backup Michael Pittman is an excellent receiver and hard-nosed runner, while fullback/H-back Mike Alstott showed that he still has the lift to get airborne at the goal line last season.

10b. Chicago Bears
Cedric Benson, Thomas Jones, Bryan Johnson
The Bears deserve to be here too considering what Thomas Jones did for Chicago last year. Jones has given the Bears two years of quality service and what does he get for his performance? Most likely a backseat to Cedric Benson this year, of course. Jones has missed some camp time because of contract demands and injury, and Benson has been resting a sore shoulder, but this unit has a great depth and will be fine with either back this year. Bryan Johnson is a tough blocker and has pretty good hands.

THE BOTTOM FIVE:

28. Indianapolis Colts
Dominic Rhodes, Joseph Addai, James Mungro
Where do you put these guys? Dominic Rhodes has been a backup his whole career and Joseph Addai should be very good, but he’s only a rookie and will split carries with Rhodes. The Colts don’t even have a true fullback, so that docks them a little bit as well.

29. Tennesee Titans
Chris Brown, LenDale White, Travis Henry, Troy Fleming
Chris Brown and Travis Henry have proven to be pretty average while rookie LenDale White has a chance to be good, he dropped into the second round due to an injury suffered on his pro day and attitude issues. Fullback Troy Fleming is the only fullback on the roster, which doesn’t bode well for competition.

30. Oakland Raiders
Lamont Jordan, Zach Crockett, Justin Fargas
LaMont Jordan deserves to be the starter for a Raiders team in desperate need of a 1,000-yard back, but Justin Fargas is injury prone and fullback Zack Crockett was the second leading rusher on the team last year with 208 yards. That’s not a good thing, by the way.

31. San Francisco 49ers
Frank Gore, Chris Hetherington, Maurice Hicks
Frank Gore made the most of his opportunities last year and finished with 607 yards on 127 carries, but we’ll find out what he’s made of this year now that he’s a full-time starter. Chris Hetherington is a bit of a journeyman.

32. New York Jets
Kevan Barlow, B.J. Askew, Cedric Houston
With the very recent trade for Kevan Barlow, Curtis Martin’s days are certainly coming to an end in New York. Barlow should be productive, but no one knows how a guy is going to respond in a new situation, especially a running back. B.J. Askew hasn’t seen much field time and although Cedric Houston showed a bit of promise at times last year, he’s got some fumbling problems and the Jets obviously don’t have much faith in him. You could easily flip-flop the Jets and 49ers, but at this point, I think Gore has more upside and he has a better backup.