Whenever Rashad Jennings goes to speak to children, he always brings a picture because they never believe what he tells them. He really was once a 270-pound, “chubby, dorky” kid with red-rimmed glasses and asthma. He used to bring “little drinks” to his high school football game so he had something to do on the bench because he was so sure he wasn’t going to play. Until one day he did. It was a remarkable stroke of luck that day that a scout from the University of Tennessee happened to be in the stands when a series of injuries forced a young Jennings onto the field during his junior year at Liberty Christian Academy in Lynchburg, Va. As unprepared as he was, he was forced to play running back and linebacker, he said, and ended up scoring two touchdowns on each side of the ball. What he learned that day is that opportunities rarely come with any warning. Or in other words, as the late John Wooden once said in Jennings’ favorite quote, “When opportunity presents itself, it’s too late to prepare.” So he did what the scout told him that day after the game: He got in shape, got his grades up from what at one point was a 0.6 GPA and got ready for the next time he was asked to play. That’s why the 6-1, 231-pounder is so ready to be the man in the Giants’ backfield right now. That was always the plan for the 29-year-old Jennings from the moment he signed a four-year, $10 million deal with the Giants in March. He was the centerpiece of the Giants’ plans to rebuild their shattered backfield, long before they had any idea whether David Wilson would be allowed to continue his NFL career. Now that Wilson’s career is over, there really is no question. The Giants’ running game belongs to Jennings. And after four NFL seasons in Jacksonville and Oakland, in which he started only 17 games and never topped the 163 carries he had last season, Jennings can’t wait to see what he can do.