The Patriots were looking for some added backfield talent as starter Sony Michel underwent offseason foot surgery and opened training camp on the active/physically unable to perform list.
Additionally, reserve back Brandon Bolden chose to opt out of the 2020 season.
Miller missed all of last season, while a member of the Houston Texans, due to a torn ACL that he suffered during the third preseason game.
Miller ran for 2,934 yards and 13 touchdowns on 716 carries, adding 92 receptions and 5 receiving touchdowns over his three active seasons in Houston.
Prior to joining the Texans in free agency via a four-year, $26 million contract, Miller played for the Miami Dolphins who selected him in the fourth round of the 2012 draft.