Barker announced his decision via Twitter Sunday and also released a 4,000-word open letter to coach Jerry Kill on his Tumbler account, the Daily reported.
Barker accused Kill of lying, psychological abuse and manipulation. He said that Kill belittled him in front of the entire team last Thursday.
Kill defended his side of the story Monday and said he was unsure why Barker quit.
Barker led the Gophers in receiving through 11 games. He had 30 receptions for 577 yards and seven touchdowns.