According to Mike Reiss of ESPNBoston, the New England Patriots felt comfortable enough with the their young running backs to allow Danny Woodhead to test free agency.
Woodhead eventually signed with the San Diego Chargers for money the Patriots didn't want to match. Reiss writes:
'It's easy to say after Danny Woodhead signed a two-year deal with the Chargers that the Patriots feel comfortable with their other options at the position -- specifically Stevan Ridley, Shane Vereen, Brandon Bolden, Leon Washington and Jeff Demps -- but I don't think it's that black and white.
The Patriots were in discussions to bring Woodhead back, which tells me this was a case where the economics drove the decision and the price tag (2 years, $3.5 million, $1 million signing bonus, with salary cap charges of $1.25 million in 2013 and $2.25 million in 2014) was deemed too rich.'