SANTA CLARA -- LaMichael James, who Sunday morning appeared poised to become the 49ers No. 2 running back because of Kendall Hunters injury, suffered a dislocated elbow in practice in the afternoon and will miss about a month.
Suddenly, the 49ers, who had one of the deepest and most intriguing running back groups in the NFL when training camp began Thursday, are thin at the position.
Rookie Carlos Hyde and seldom-used Jewel Hampton are the only healthy runners behind starter Frank Gore. They split nearly all of the repetitions Sunday after James went down early in practice.
Another tailback, Marcus Lattimore, began camp on the non-football injury list. Saturday, general manager Trent Baalke said Lattimore was close to joining practice but did not have a timeline for his return.
Baalke insisted Lattimore, who is coming back from reconstructive knee surgery, has not had a setback.
Hes coming off, as we all know, a horrific injury, Baalke said. And we want to make sure, as does he, that hes 100 percent mentally and physically ready to go to help this football team, and to give himself the best chance to compete at a high level. ... But as far as setbacks, no.
James, a second-round draft pick in 2012, was going against inside linebacker Michael Wilhoite in a blitz pick-up drill when he was blown backward and immediately went to the ground clutching his left arm. He was carted off the field.
James suffered an ankle injury in the 2012 preseason and sprained a knee ligament in last years preseason. Both injuries caused him to miss the early part of the regular season and drop on the depth chart.
He also suffered a dislocated right elbow in 2011 at Oregon. After missing two games, he carried 13 times against Washington State.
If James misses a month, he would be back a week before the regular-season opener Sept. 7 at Dallas.
Asked about James as a possible replacement for Hunter earlier in the day, coach Jim Harbaugh said, We have complete and total confidence in LaMichael James.
We know him to be a very fine football player, he said. I think if you look at where he was at last year at this time in training camp, he got a MCL injury that kept him out of action for quite a while and affected where he was on the depth chart. And then eventually he got his chance, but he was right in this same mix last year at this time. Hes on familiar ground. He knows the team has always counted on him to be a top football player at the highest level.
Two days earlier, Hunter suffered an ACL tear when his right knee buckled after a short completion. Hunter remains on the active roster, although the 49ers surely will have to add bodies at running back to get them through training camp.
James also is the teams top punt returner. Devon Wiley (Granite Bay High School), Perrish Cox and Quinton Patton also have practiced at the spot. Rookie wide receiver Bruce Ellington likely will get a chance to return punts, too, after he recovers from an ankle injury.
Rookies activated The 49ers moved two draft picks, outside linebacker Aaron Lynch (hamstring) and center Marcus Martin (ankle), off injury lists and onto the active roster.
Lynch, a fifth-round pick, will compete with Dan Skuta, Corey Lemonier and Chase Thomas for repetitions behind starters Aldon Smith and Ahmad Brooks. Martin, a third-round choice, is the top backup at center behind Daniel Kilgore and could get some repetitions at right guard behind Joe Looney.
Being on the active roster doesnt necessarily mean Lynch and Martin will immediately rejoin practice. Ellington, a fourth-round pick, was activated Friday so he could participate in morning walk-throughs. He is close to rejoining the full practice.
Read Matt Barrows blogs at www.sacbee.com/sf49ers.