McCown tore the anterior cruciate ligament in his right knee at San Diego on Sunday. McCown replaced benched starter David Garrard in the fourth quarter and injured his knee on a 4-yard scramble with less than a minute remaining. Garrard came back in and threw a touchdown pass to Mike Sims-Walker that made it 38-13.
Without McCown, the Jaguars will spend Tuesday working out quarterbacks. Jacksonville has Brett Ratliff on the practice squad, but coach Jack Del Rio says he's not ready to step into the backup role.
McCown completed 11 of 19 passes for 120 yards against the Chargers, most of it coming against a prevent defense.