Due to the surprise retirement of Branden Albert, the Jacksonville Jaguars roster had an open slot. There are some high profile free agents still available but Jacksonville chose to replace Albert with Tyler Gaffney per jaguars.com.
The possibility of Gaffney becoming the starting running back is highly unlikely. According the Jaguars.com press release:
After signing with New England, Gaffney spent the 2014 on the team’s reserve/injured list after sustaining a knee injury in training camp. In 2015, Gaffney was again placed on New England’s reserve/injured list for the season.