With their starter struggling and the score out of reach, the Jaguars pulled quarterback David Garrard and inserted backup quarterback Luke McCown for the fourth quarter.
Two plays from the end of the game, McCown scrambled inside the 5-yard line and fell on his right knee. The Jaguars did not know the extent of McCown's injury, but he wore a sleeve on the leg after the game.
McCown will have an MRI to determine the seriousness of the injury.
"We'll see," McCown said as a Jaguars trainer placed a black brace on his knee. "I'm not a doctor."
He tore the anterior cruciate ligament in that knee in 2006. It's unlikely this injury is the same because McCown was walking on his own power after Sunday's loss to San Diego.