MINNEAPOLIS — Adrian Peterson was suspended without pay for at least the rest of the season by the NFL on Tuesday.

The league said it informed the Minnesota Vikings running back in a letter from Commissioner Roger Goodell that he will not be considered for reinstatement before April 15 for violating the NFL personal conduct policy — the first example of the league’s crackdown on players involved with domestic violence.

The NFL Players Association quickly announced its plan to appeal, sharply rebuked the league’s alleged inconsistency and unfairness in the process. The NFL’s words were even stronger, with a nearly 1,600-word statement spelling out his path to a return to the field and describing the reasons for the punishment.

Peterson pleaded no contest Nov. 4 to misdemeanor reckless assault in Texas for injuries to his 4-year-old son with a wooden switch. He said he intended no harm, only discipline. Peterson was on a special exempt list at the sole discretion of NFL Commissioner Roger Goodell, essentially paid leave while the case went through the legal system.

The NFLPA said Peterson was told that would count as time served for any suspension levied, citing an unnamed NFL executive. League spokesman Brian McCarthy said by email the stay on the exempt list was taken into account.

“There were aggravating circumstances that led to the discipline announced,” McCarthy said.

Peterson’s salary for the season was $11.75 million. He will keep the pay accrued while on the exempt list.

Peterson’s agent, Ben Dogra, told The Associated Press he and his client were scheduled for a conference call Tuesday with the NFLPA to discuss options.

“We look forward to filing an immediate appeal and coming to a resolution for Adrian Peterson that would be appropriate under the circumstances,” Dogra said.

The Vikings don’t practice Tuesdays. The organization issued a brief statement: “We respect the league’s decision and will have no further comment at this time.”

Goodell announced on Aug. 28 that the league would toughen punishment for players involved with domestic violence. That action stemmed from a torrent of criticism for the initial leniency toward Baltimore Ravens running back Ray Rice following a caught-on-camera knockout punch of the woman who is now his wife.

The Vikings (4-6) have six games left this season. The league’s enhanced policy calls for a six-game suspension for first offenses of assault, battery or domestic violence. Aggravating circumstances warrant higher levels of discipline, and Goodell’s letter to Peterson spelled that out.

Goodell pointed to the child’s age and the significant physical difference between Peterson and his son.

“Further, the injury inflicted on your son includes the emotional and psychological trauma to a young child who suffers criminal physical abuse at the hands of his father,” Goodell wrote. “Second, the repetitive use of a switch in this instance is the functional equivalent of a weapon, particularly in the hands of someone with the strength of an accomplished professional athlete.”

Goodell also came down on Peterson for showing “no meaningful remorse” for hurting the boy and expressed concern that he “may feel free to engage in similar conduct in the future.”

The union has accused the league of overstepping bounds spelled out in the collective bargaining agreement.

“The decision by the NFL to suspend Adrian Peterson is another example of the credibility gap that exists between the agreements they make and the actions they take. Since Adrian’s legal matter was adjudicated, the NFL has ignored their obligations and attempted to impose a new and arbitrary disciplinary proceeding,” the NFLPA said.