Marcus Lattimore's comeback from a knee injury suffered over two years ago may come to an end soon, as ESPN's Adam Caplan reports the San Francisco 49ers running back decided to retire from the sport due to issues with his knee, although that hasn't been confirmed.

According to Ian Rapoport of NFL Network, Lattimore is still weighing his options and his agent, Michael Perrett, insists that the running back hasn't made a decision yet about his future in football.

Lattimore, 23, practiced for the first time ever with the 49ers last week well over a year after the team selected him in the fourth round of the 2013 NFL Draft. As a rookie, Lattimore spent the entire 2013 season on the reserve/non-football injury list rehabbing a knee injury suffered in October 2012.

However, after Lattimore's return to the practice field for the first time in over two years, the running back experienced soreness in his surgically repaired knee, according to CSN Bay Area's Matt Maiocco.

Lattimore originally suffered a torn ligament in his knee as a sophomore at South Carolina in 2011 before suffering a devastating injury in his opposite knee one year later that included a dislocation and significant damage to multiple ligaments. It proved to be his final season with the Gamecocks after Lattimore declared for the 2013 NFL Draft at the end of the season.