Merle Lee, 35, of Newton was charged with aggravated assault after the victim's condition worsened, said State Police Sgt. Brian Polite. He had initially been charged with simple assault.
James Mohr, 23, of Queens, N.Y., was taken out of intensive care and listed in fair condition Wednesday at Hackensack University Medical Center.
Mohr got into a brief scuffle with some guys and the skirmish broke up on its own, Polite said.
Lee then "came out of the blue and punched Mohr in the face," Polite said.
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The state police sergeant said one of the fans in the initial group had on a Chiefs jersey but that witnesses said the incident "was not a Jets-Chiefs melee."
The operators of MetLife Stadium said Lee was immediately arrested.
"This is an unacceptable attack on one of our guests and we have been working with the New Jersey State Police to make sure the man arrested is prosecuted to the fullest extent of the law," MetLife officials said in a written statement.
Both security guards and New Jersey State Police work each game, they said, adding that arrests in the parking lot occur on average only every four games.
The Jets also released a statement.
"We have reached out to James to wish him a speedy and full recovery. Our organization works hard to provide fans with a safe and secure environment and there is no place for this type of behavior. We are working with the stadium and New Jersey State Police to be certain that any and all perpetrators are prosecuted to the fullest extent of the law."