Robinson was drafted in the 4th round of the 2006 NFL Draft by the San Francisco 49ers. The 49ers converted him into a running back. 49ers head coach Mike Nolan was immediately impressed with Robinson's attitude and toughness during training camp. After a solid preseason, Robinson rose up to the number two running back position behind Frank Gore on the depth chart. After Robinson scored his first and second career touchdowns against the Philadelphia Eagles and veteran pro-bowl safety Brian Dawkins for one of them, knocking Dawkins out of the game, in week 3, Mike Nolan indicated that he intended to use Robinson more often in goal line situations. Despite Nolan's statement, Robinson's playing time actually would decrease over the course of the season, and he did not score another touchdown. He finished the year with 38 carries for 116 yards, 9 receptions for 47 yards, and 2 touchdowns.