Harrison is starting his second stint with the Eagles. He was first acquired in a 2010 trade with Cleveland and rushed for 239 yards and a touchdown.
Brown had only 13 carries for 38 yards with the Eagles. His fumble against San Francisco cost Philadelphia a win.
Harrison had only 14 carries for 41 yards with the Lions. In 2009, Harrison led the Browns with 194 carries for 862 yards and five touchdowns, and tied for the team lead with 34 receptions for 220 yards and two touchdowns.
Both running backs have fallen out of favor with their teams and had little playing time.