The two-year-old son of Minnesota Vikings star running back Adrian Peterson died in hospital Friday from injuries received in an alleged assault, US media reported.
USA Today and celebrity news website TMZ reported the boy had died, hours after news broke that he had been hospitalized in critical condition.
TMZ said the child had been on life support since Thursday evening, and was taken off a ventilator at the hospital in Sioux Falls, South Dakota, on Friday.
Prior to the boy's death, Joseph Robert Patterson, 27, had reportedly been arrested on two counts of aggravated domestic assault and aggravated battery of an infant.
The Vikings said on their website that Peterson had rejoined the team on Friday after traveling to South Dakota to deal with the matter.
Peterson spoke to reporters on Friday, but declined to discuss specifics about his son.
"I really appreciate all the support that I've been receiving from fans, the Vikings organization," Peterson said.
"This is a private matter and I would ask you all to please just respect my privacy and not ask at all about the situation at hand. Thanks."
Peterson, who holds the record for the most rushing yards in a single National Football League game with 296, said he would play for the Vikings on Sunday against Carolina.
"I will be playing Sunday ... without a doubt," said last year's league MVP.
The child was at Patterson's home in Sioux Falls when he was injured, USA Today reported.
The boy had recently moved to the home with his mother.
Patterson has a history of domestic abuse against his own son and the boy's mother, also from Sioux Falls, the paper said, citing court records.
Peterson has been selected to the Pro Bowl game five times and won two NFL single season rushing titles in 2008 and 2012. The Vikings' seventh overall pick in the 2007 entry draft, he was named MVP of the Pro Bowl game in 2007.
Peterson has carried the ball 92 times for 421 yards and five touchdowns in four games for the Vikings this season.