Forty-five seconds into one of his least favorite All-Star weekend activities, Tim Duncan’s response was interrupted from afar during a mandatory Friday morning session with reporters peppering him with questions both perceptive and inane. “How are you doing, old man,” former Spurs forward Robert Horry shouted across a hotel ballroom overflowing with inquiring minds. “What’s up?” Duncan shouted back to “Big Shot Rob,” the seven-time NBA champion who helped the Spurs win their third and fourth NBA titles in 2005 and 2007 before retiring in 2008, at age 37, after five seasons in silver and black. “Can you still walk?” Horry said, punctuating the question with a cackle. “A little bit,” Duncan said. “Just a little bit, but I’m still younger than you, buddy.” Horry’s question about Duncan’s ambulatory skills was hardly impertinent. He knew the Spurs captain sat out the first four games of the rodeo road trip after Washington’s Martell Webster rolled into the back of his legs in a game at the AT&T Center on Feb. 2, sending the Spurs captain sprawling to the floor in pain. Clutching the left knee that has been an occasional bother since surgery was required to repair torn cartilage late in the 1999-2000 season, Duncan wasn’t thinking about the ? significance of being selected for his 14th All-Star Game a year after being left off the Western Conference roster, a first for his career.