Patriots free-agent fit: Running back

Fourth in a multipart series on free-agent fits at various positions leading into the start of free agency March 10.

Position: Running back

Players under contract for 2015: LeGarrette Blount (2015), Jonas Gray (2015), Brandon Bolden (2016), James White (2017), Tyler Gaffney (2017), Dion Lewis (2015)

Level of need: Moderate to high

Projected top targets: Reggie Bush (Lions), Stevan Ridley (Patriots), Pierre Thomas (Saints), Shane Vereen (Patriots)

Why Bush fits: He just turned 30 and had one of his best seasons in the NFL playing under current Patriots assistant coach Brian Daboll in Miami (2011) when Daboll was offensive coordinator. He's one of the best pass-catching running backs on the market, and if Vereen signs elsewhere, he looks like the best possible replacement if the Patriots want to bring in a veteran as a possibility for that role. One of the main knocks on him at this point of his career is missing time due to injury.

Why Ridley fits: He knows the system, has proven capable as a top power option, and has said he feels like he has something to prove in 2015. While likely going to have to settle for a one-year contract to set himself up for another crack at free agency next year (because of a torn ACL on Oct. 12), one question will be if it's a good match for Ridley and the Patriots in the sense that the team has a history of rotating its backs.

Why Thomas fits: With 77 receptions in 2013 and 45 in 2014, he's one of the NFL's better pass-catching backs. He turned 30 in December and has spent all eight seasons of his NFL career with the Saints.

Why Vereen fits: In an offense that trends to the pass, Vereen's role as the "passing back" had him playing 52.9 percent of the offensive snaps in 2014. He runs precise routes, has reliable hands, is a willing and capable pass-protector, and is a top-notch locker-room presence.

Other names of note: Justin Forsett (Ravens), Frank Gore (49ers), Roy Helu (Redskins), Mark Ingram (Saints), Darren McFadden (Raiders), DeMarco Murray (Cowboys), Ryan Mathews (Chargers), C.J. Spiller (Bills).

Market conditions: Viewed as the deepest position in the draft by analysts, while free agency also is deep, creating an overflowing market.

Running back-based questions: Will Vereen be wooed in free agency by another team that ups the bidding to a level the Patriots aren't comfortable matching? Is White, the 2014 fourth-round pick out of Wisconsin, a viable replacement as the pass-catching back if that happens? Does Ridley view a fresh start as his best option, or is a return to New England preferred? Does Gray become a bigger part of the plans in 2015 after slipping off the radar following the acquisition of Blount and being late to a meeting? Will Gaffney challenge for a role after the sixth-round pick out of Stanford was claimed on waivers from the Panthers last year?