Adrian Peterson‘s 2-year-old son is currently in critical condition in a South Dakota hospital … after he was allegedly severely beaten by the man dating the mother of his child, TMZ has learned.

The Minnesota Vikings running back immediately left his team to be with his son.

Officials tell us they’ve arrested the suspect, 27-year-old Joseph Patterson … who’s been charged with aggravated felony assault and battery of an infant.

According to law enforcement, emergency responders arrived to the apartment where Peterson’s son was living at 5:46 PM on Wednesday … and found...continue to story...click here!