Running back Kendall Hunter is expected to be out for the remainder season with an ankle injury he sustained in the third quarter of the 49ers' victory Sunday against the New Orleans Saints.The 49ers have yet to reveal the extent of Hunter's injury, but USA Today, citing a person informed of the prognosis for Hunter, reported that it is a season-ending injury.That likely means the 49ers will activate undrafted rookie Jewel Hampton to the 53-man roster.The 49ers had to make a roster move with Hampton, who was at the end of his three-week window after coming off the team's reservenon-football injury list. He underwent offseason surgery to remove bone spurs from his left foot. Hampton is expected to add depth at running back, as well as be available to help on special teams.The loss of Hunter is a huge blow to the 49ers' offense. Hunter, a second-year pro, was the 49ers' second-leading rusher behind Frank Gore. Hunter gained 371 yards and two touchdowns on 72 rushing attempts for a 5.0 average.With Hunter out of action, Brandon Jacobs or Anthony Dixon is likely to be used as Gore's backup. The 49ers might activate rookie running back LaMichael James, as well.The 49ers have another roster spot to fill, as Kyle Williams sustained a torn anterior cruciate ligament on the same play in which Hunter was lost.The 49ers already have five wide receivers, so there's not a need to add another. Instead, special teams is the area in which the 49ers are expected to turn for him. The club is expected to choose between practice-squad players safety Michael Thomas, linebacker Michael Wilhoite and receiver Ricardo Lockette for a spot on the 53-man roster.The 49ers will sign receiver Chad Hall to the practice squad, a league source told CSNBayArea.com on Tuesday.