Arizona’s rushing success starts with freshman running back Nick Wilson, who is second in the Pac-12 with 449 rushing yards and 6.8 yards per carry. Cal’s defense ranks first in the conference in fewest rushing yards allowed per game, although that ranking might be inflated by having played Northwestern and Sacramento State, teams that don’t have powerful run games. [...] Arizona provides a test that Nickerson calls a middle linebacker’s dream, a vision that could become a nightmare if the Wildcats steamroller the Bears’ defense. Starting defensive tackle Austin Clark missed the Sacramento State game with a sore knee. [...] the bye week allowed Clark, along with backup safety Avery Sebastian (quad) and cornerback Darius White (shoulder), to return to full health.