Montalvo, a freshman who had recently been promoted to the travel team as a third-string quarterback, was in critical condition at Kendal Regional Medical Center, The Baltimore Sun reported.
Police have not released a report on the collision but Navy Coach Ken Niumatalolo said Montalvo family members told him Montalvo was a passenger in a car driven by a friend who took a wrong turn in thick fog and crashed the car into a house. Niumatalolo said it was his understanding the driver was also hospitalized in a coma, the newspaper reported.
Niumatalolo said he visited Montalvo Saturday and the player was "doing well" at the time, but he said Montalvo took a turn for the worse Monday.
Dr. Jeff Fair, director of sports medicine at the academy, said hospital medical staff had told academy doctors Montalvo had developed an infection that was driving up his blood pressure.
"He's going to be in the hospital quite awhile, I know that," Fair said.
Offensive coordinator and quarterbacks coach Ivin Jasper said the Middies -- who are preparing for their traditional game with the U.S. Military Academy Dec. 8 -- were "struggling" with the situation.
"He's just a great kid and you hate to see something like that happen to good people," Jasper said. "We're keeping him in our prayers."