49ers RB Kendall Hunter will miss the rest of the season with a torn Achilles tendon. (US Presswire)

San Francisco 49ers RB Kendall Hunter is expected to be placed on injured reserve as a result of a torn Achilles tendon he suffered in Sunday’s game against New Orleans, according to a report from Matt Barrows of the Sacramento Bee. The injury, which occurred on the same play WR Kyle Williams tore his ACL, was originally believed to be an ankle injury.

With both players out for the season, rookies WR A.J. Jenkins and RB LaMichael James are strong candidates to be active Sunday against St. Louis. Jenkins, the team’s first-round pick, has been active for only one game this year, but did not play. James, the team’s second-round pick, has been inactive all season.

There are seemingly four candidates for three spots. FB/DL Will Tukuafu was inactive for the first time this season on Sunday, replaced by RB Brandon Jacobs. The team could have both players active against the Rams, leaving only one spot for either Jenkins or James.

Then there is the possibility that the team leaves Jacobs inactive, with the rationale being that James is more comparable to Hunter.

If the team was happy with its active roster against the Saints, Tukuafu could be the odd man out with James replacing Hunter and Jenkins replacing Williams.

Another option is former Eagles WR/returner Chad Hall, who was signed to the team’s practice squad Tuesday, according to multiple reports. Hall could be viewed as an immediate option as a backup kick returner to Ted Ginn Jr.

The injuries also leave two spots to fill on the 53-man roster.

If the team wants to keep its position breakdown the same, rookie RB Jewel Hampton could replace Hunter and WR Ricardo Lockette could be moved up from the practice squad to replace Williams. It’s unlikely whoever is added to the 53-man roster would be active on game day.

Hunter was having a good season as the primary backup to RB Frank Gore. He ran for 371 yards on 72 carries (5.2 ypc) with a pair of TDs.

Follow 49ers reporter Kyle Bonagura on Twitter @CBS49ers and @KyleBonagura.