For the first time in his 12-year career, 49ers defensive end Justin Smith is doing something new. Now he’s the guy coming back from injury. Smith had surgery to repair a half-torn triceps tendon after the Super Bowl; it was an injury he sustained Dec. 16 in the 49ers’ 41-34 win in New England. Smith will be 35 on Sept. 25 and is entering the final season of his six-year, $45 million deal with the team. Previously, Smith said he could play another three or four years. But now, it’s a one-year at a time proposition.