SAN FRANCISCO (AP) — Tony Vitello fully recognizes he is a most unconventional call-up to Major League Baseball, making the leap from the college coaching ranks at Tennessee to the San Francisco Giants while bypassing the minor league farm system. Yet Vitello hardly seems fazed by the pressures of taking such a daunting path — “this is a challenge that has been presented to me,” he said Thursday. He plans to get into spring training drills right away alongside his Giants team, throwing batting practice or hitting fungoes in an effort to help improve some fundamentals.