Star Michigan defensive back Will Johnson left Saturday’s game against USC in the fourth quarter and was seen walking up the tunnel on the CBS broadcast. And shortly after, a more concerning update emerged. Johnson’s family apparently followed him up the tunnel a short while later, according to CBS sideline reporter Jenny Dell. The group then apparently turned left prior to the locker room entrance, heading toward the on-site X-ray facilities. CLICK HERE to go to PrizePicks and use code ON3 to receive a guaranteed $50 once you play $5 in lineups! Michigan held a 20-17 lead over the Trojans whe…