Their leader at safety left for the NFL. A starting cornerback followed. Their usual nickel corner was out for spring. The replacement tore a knee ligament last Tuesday. So as USC began scrimmaging on Saturday afternoon, with its secondary in somewhat rough shape, Isaiah Pola-Mao walked up from his usual perch at safety to line up in the slot, settling into his new, albeit temporary place at nickel. There aren't many other options at cornerback.Not after USC lost Max Williams for the year to a torn anterior cruciate ligament in his knee. Greg Johnson, who opened last season as the starting nickel, isn't expected to return from his own knee injury until fall either. Until Saturday, USC didn't even have its top corner, Chris Steele, due to health and safety protocols. "Isaiah's been in the system," USC coach Clay Helton said. "He understands it, and it just helps him grow also and puts some tools in his toolbox by being so versatile." Pola-Mao will likely revert to safety when Johnson returns in the fall. But for now, his move to nickel will open up plenty of chances for the four safeties who signed on early to fight for playing time. - Los Angeles Times