Fresno State senior linebacker Tim Skipper wears number 51, not because Dick Butkus wore it but because Sam Mills did. The 5'9", 229-pound Mills ignored those who doubted he'd succeed in the NFL because of his size by becoming an All-Pro with the New Orleans Saints and the Carolina Panthers. If Mills, who played at Montclair ( N.J.) State, bent the rules on minimum dimensions for linebackers, the 5'7", 200-pound Skipper broke them. Skipper made the 34th start of his career last Saturday, against Cal, and his 12 tackles moved him into second place (329) on the Bulldogs' alltime list. His knowledge of the game comes from his father, Jim, a former NFL assistant and now coach of the San Francisco franchise in the soon-to-debut XFL. Tim has designs on a pro career, and if he doesn't follow in Mills's footsteps, he might be the ideal candidate for the unconventional new league.