MINNEAPOLIS — Adrian Peterson’s potential return to the Minnesota Vikings is at the heart of a dispute between the NFL and the players’ association, and the star running back thinks the league is being unfair.

Peterson criticized the NFL on Sunday over the process of being activated from a special exempt list after he pleaded no contest Nov. 4 to misdemeanor reckless assault in Texas for hitting his 4-year-old son with a wooden switch.

The union filed a grievance with the league, demanding Peterson be allowed to rejoin the Vikings until the determination of any punishment under the personal conduct policy. The NFL, however, ruled Peterson must remain on paid leave in the meantime.

Commissioner Roger Goodell has the sole power to remove him from the special exempt list.

“At this point, I’ve resolved my matter in the criminal court; I’ve worked to make amends for what I’ve done; I’ve missed most of the season, and I stand ready to be candid and forthcoming with Mr. Goodell about what happened,” Peterson said in a statement issued by the NFL Players Association.

“However, I will not allow the NFL to impose a new process of discipline on me, ignore the CBA, ignore the deal they agreed to with me, and behave without fairness or accountability. The process they are pushing is arbitrary, inconsistent, and contrary to what they agreed to do, and for those reasons, I never agreed to the hearing.”

The NFL offered Peterson the hearing, but a hearing is only required by the CBA if a player elects to appeal a punishment. In this case, no decision has been made yet on discipline. The NFL’s enhanced penalty for players involved in domestic violence, announced by Goodell in August, is a six-game suspension. The injuries to Peterson’s son occurred in May.

The league had no further comment Sunday.

In the statement, Peterson said the NFLPA sent repeated questions to the NFL about the nature and purpose of the hearing that went unanswered.

“After consulting with the union, I told the NFL that I will attend the standard meeting with the commissioner prior to possible imposition of discipline, as has been the long-term practice under the CBA, but I wouldn’t participate in a newly created and non-collectively bargained pre-discipline ‘hearing’ that would include outside people I don’t know and who would have roles in the process that the NFL wouldn’t disclose,” Peterson said.

Regarding the grievance, an arbitrator was scheduled to hear arguments from both sides Monday. That’s only to determine whether Peterson should be immediately reinstated prior to the league’s issuance of any discipline. He could, in theory, be ordered back to the team only to be suspended soon after.

But as Minnesota played Chicago Sunday, time was running out on this season for the 2012 NFL MVP. The Vikings have six games left after this weekend.