SANTA CLARA -- On a day in which the 49ers signed NaVorro Bowman to a five-year extension that will keep the All-Pro linebacker under contract through 2018, they sprang a few short-term leaks elsewhere on the roster.
Running back Kendall Hunter and wide receiver/return man Kyle Williams were placed on injured reserve Tuesday, ending the season for two valuable role players. Hunter (torn left Achilles) and Williams (torn left ACL) were hurt on the same third-quarter play on Sunday in New Orleans.
The injury news was a blow to the 49ers locker room as players prepared for this weekend's game against the St. Louis Rams. Running back Frank Gore was disappointed to see the season end for his understudy, who was second on the team with 72 carries for 371 yards.
"That's a big loss," Gore said. "Everybody on the team respects his game. Kendall is a player who can make a big play any time in the game."
It's unclear who will inherit Hunter's carries, but speculation Tuesday focused on second-round pick LaMichael James. A two-time consensus All-America selection at Oregon, the rookie has yet to take a regular-season snap.
Teammates say James is ready.
"I expect dynamic plays, man," running back and special teamer Anthony Dixon said. "I watch him every day on the practice field, and he's making plays, going up to get the ball. ... His gears, the way he's so shifty -- it's crazy."
A year ago, James averaged 150.4 rushing yards per game and ranked second in the NCAA with 1,805 yards. At just 5-foot-9, 195 pounds, he reminds 49ers safety Donte Whitner of a player he just faced in New Orleans
"He's a guy similar to (Darren) Sproles," Whitner said. "He can still carry the ball up inside. I know he's anxious to get out there and play."
Another option for the No. 2 running back spot is Brandon Jacobs, an eighth-year veteran whose season was derailed by a knee injury during training camp. Jacobs, who said he is healthy again, had seven rushing touchdowns for the New York Giants a year ago.
The 49ers also activated running back Jewel Hampton, who had been on the non-football injury list since Aug. 27. Originally signed as an undrafted free agent, Hampton was the conference newcomer of the year while at Southern Illinois in 2011.
Replacing Williams will also take creativity, since he was the team's No. 3 receiver and also shared time with Ted Ginn Jr. as the returner for punts and kickoffs. His injury might open the door for first-round pick A.J. Jenkins to make his debut. The 30th overall pick last April has yet to take a snap.
"A.J. is an extremely talented guy," Whitner said. "He's been getting better and better as he's been going against the first-team defensive backs in practice. He's actually made some plays on us, and made some big plays. So, I know if he's called upon he's going to be ready to go also."
At least on one side of the ball, there are no such question marks. The 49ers announced a deal for Bowman that will keep him under contract through 2018. As the team noted, all four starting linebackers are under contract through at least 2015 -- Ahmad Brooks (2017), Patrick Willis (2016), Aldon Smith (2015) and Bowman (2018).
According to figures first reported by NFL.com, Bowman's contract is worth $45.25 million, with $25.5 million in guaranteed money,
"NaVorro epitomizes what we look for in a 49er," general manager Trent Baalke said in a statement emailed to the media. "We are excited that the All-Pro tandem of Willis and Bowman will be together in red and gold for years to come."
Bowman leads the 49ers (and ranks sixth in the league) with 100 tackles and is coming off a season in which he emerged as one of the premier linebackers.
"That's not here. We're a team," Gore said. "That's one thing about our locker room. We're one. We're all as one. If it's Alex, we're going to be behind Alex. If it's Kap, we're going to be behind Kap."
49ers (8-2-1) at St. Louis (4-6-1), 10 a.m. FOX