49ers' Marcus Lattimore to retire

— -- San Francisco 49ers running back Marcus Lattimore is planning on retiring from the NFL because of knee issues, a league source confirmed to ESPN.

Lattimore's agent, however, denies that his client's NFL career is over.

"Info being reported is not accurate," Michael Perrett told ESPN NFL Insider Adam Schefter in a text message. "Marcus Lattimore has made no decision on his future."

Lattimore, 23, was not with the team during Sunday's home game against the St. Louis Rams.

"Did not see Marcus," 49ers coach Jim Harbaugh said after the game in response to Lattimore's absence. "I'm sure we'll have an announcement about that."

Lattimore spent the entire 2013 season on the non-football injury list and remains on that list this season. However, he did begin practicing last week with the hope that he would be able to play later this season.

The 5-foot-11, 220-pound back suffered serious knee injuries in 2011 (he tore the ACL and MCL in his left knee) and 2012 (right knee) during his time at the University of South Carolina.

Lattimore was a fourth-round draft pick of the Niners although his college career ending with the devastating injury in 2012 that tore every ligament in his right knee and dislocated the kneecap. He was a potential first-round draft pick but sat until San Francisco selected him 131st overall as his rehab was already underway.

After the day of practice with the Niners, Lattimore said he has embraced his lot as a role model for athletes who have suffered knee injuries and said his faith and talks with his mother and sister helped him through bad days.

"And there were a lot of bad days," he said. "Just talk to people. Don't keep it in."

ESPN.com's Paul Gutierrez contributed to this report.