Marcus Lattimore’s 49ers debut is still months away, but the rookie running back at least will get a chance to practice with his teammates this season. Jim Harbaugh confirmed Friday that Lattimore, a fourth-round pick who has been on the non-football injury list, will begin a 21-day period next week in which he can practice with the team. “He’s a hard worker. He’s a willing, willing participant in anything he’s asked to do,” Harbaugh said. “I think it will be a great step for him.” But Harbaugh reiterated that the 49ers have no plan to activate Lattimore this season. The running back didn’t seem to care. He suffered a devastating injury – a dislocated right kneecap and three torn knee ligaments – while playing for South Carolina on Oct. 27, 2012. He’s accepted the 49ers’ long-term approach for his recovery, but he also has said the reward for the monotonous rehabilitation work he’s been doing would be to practice with his teammates. “It would be important to have my mind ready for the next year – real excited about it,” he said. Lattimore said he’s been running at full speed, cutting like an NFL running back and picking up as much as he can from Frank Gore and Kendall Hunter and position coach Tom Rathman in the running backs meeting room. “I’ve learned more in these four months than I’ve ever learned as far as how the defense plays, how to read fronts, how to read linebackers, coverage ... ,” Lattimore said. “(I’ve learned) so much about the game in the last four months, (more) than I’ve learned in the last 18 years. So it’s been big.” Lattimore is viewed as a possible heir to Gore, who has one more year on his contract, in the role of workhorse running back.