A judge will determine whether 28-year-old Matthew Hinson should be sentenced to life in prison.
Hinson entered the change of plea on Tuesday.
Hinson was charged with slashing William "Christopher" Pettry's neck with a pocket knife during a bar fight last October, the night before the game.
Pettry, 42, was visiting Jacksonville to watch the Bears-Jaguars game with a friend who said Hinson had joined them at the table before the stabbing.
Prosecutors had argued that Hinson became jealous when he saw Pettry speak with his wife.
Hinson was scheduled to go to trial on July 22.
Pettry left behind a wife and three children.