DeAngelo Williams (CAR)
Until his season-ending injury last year, Williams was considered by many to be a top five talent at the position. He averaged more than 5 yards per carry from 2007 through 2009 and scored 20 times in 2008. The Panthers have a pair of capable running backs on their roster and have many more glaring needs to fill than RB, so Williams is likely to be available. He will still command a sizeable contract that could scare New England off, but if the Patriots decide to make a splash in free agency, Williams could be an attractive option.
Pierre Thomas (NO)
Thomas was an important piece of the Super Bowl puzzle for the Saints in 2009, and at just 26 years old, he should be a tremendous value for any team that signs him this offseason. He's averaged 4.7 yards per carry over the course of his career, and he is a tough runner for his size. He is also an effective receiver out of the backfield and could help keep opposing defenses guessing. He could be the homerun threat that New England's backfield has been missing in recent seasons.
Ronnie Brown (MIA)
The Dolphins may look to get younger at RB next year, so it's very possible that Brown will test the free agent market this offseason. At age 29 with just 1128 career carries, Brown should still have some gas in the tank. He struggled mightily with the Dolphins last year, but some of that might have been due to gameplanning by opposing defenses (Chad Henne wasn't scaring anyone besides Dolphins fans). Still, his down year and injury history means he probably won't command a huge investment on the open market.
Ahmad Bradshaw (NYG)
Bradshaw is probably the least likely of the free agent running backs to hit the open market, but the possibility exists since the Giants announced they would not use the franchise tag. He is a strong runner and effective pass-catcher out of the backfield. He has low mileage and held up well last season despite seeing more than 300 touches. He should command a sizeable contract, which could present a challenge for the Pats. It's unlikely that New England would win the bidding for one of the biggest prizes of the offseason.
Derrick Ward (HOU)
Ward did not live up to his pricey contract with the Bucs, but he did well in a reserve role behind the league's leading rusher in Houston last year. Ward is good out of the backfield and an effective option in the red zone. He shouldn't command a big contract this offseason, so he would make sense as an option to provide better depth. Although his age (30) is a red flag for some teams, he is a low-mileage back with plenty of experience. He could end up being the steal of the free agency period this year.