Green Ellis was retained for this season after being a restricted free agent in the off-season. This was despite the team drafting two running backs in June and re-signing Kevin Faulk also. The Patriots have a logjam at running back but Green-Ellis specialty in the short yardage game and the fact that he has proven the most of any back (outside of Kevin Faulk who likely won't be on the roster) will assure him his place on the roster and assure him of substantial touches throughout the year.
The Hard Knocks' star and former New York Jet will be looking to repeat his performances of last season. While Green-Ellis is the bruiser, Woodhead is everything but. Woodhead fits perfectly into the Patriots system and gives the team another receiver coming out of the backfield. He is incredibly shifty and elusive with reliable hands. That being said he still averaged 5.6 yards per carry last season also. Woodhead can run the ball and while he is not as physically punishing as Green-Ellis he is able to make his presence felt.
Ridley was the second of the team's drafted running backs this year but has been the star of pre-season so far. Ridley combines the strength of Green-Ellis with the elusiveness of Woodhead. At 22 years of age his transition to the professional game has been impressive. He averaged 4 yards per carry on his debut with three touchdowns total before averaging 6 yards per carry in his second appearance versus the Tampa Bay Buccaneers.
Vereen has yet to get on the field in pre-season with the Patriots and is behind the curve as far as being ready for the season. His roster spot is most likely safe however as he was drafted in the second round of this year's draft. He has recently returned to practice and will be hoping to feature in at least one of the final two preseason games.