Eden Prairie, MN (SportsNetwork.com) - Adrian Peterson is back with the Minnesota Vikings for the first time in almost nine months and says his return to the team went "smooth."

Peterson returned for organized team activities on Tuesday after missing last week's initial spring workout sessions due to friction with upper management.

"I had a long time to really think about things and ultimately what it came down to was getting back in the building," Peterson said.

"I've been working really hard to keep my body in shape and it came down to getting back in the building, being around my teammates, being around the coaches and getting back into the swing of things," he said. "So I reached out and gave them a heads up that, hey, I'll be in town and I'll be coming in."

Peterson missed nearly all of last season after he was indicted in Texas on charges of reckless or negligent injury to a child, having admitted to hitting his 4-year-old son with a tree branch last May.

On Tuesday, Peterson, who has been undergoing counseling, said he "made a mistake."

"I know a lot of people don't view it that way based on what they've seen, but ultimately that's what it was and my son knows that," he said. "He knows I love him and my other kids know the same."

Peterson said the first person he apologized to was his son.

"And that was right after the situation took place and I realized what happened," he said. "I apologized for the mistake that I made. It wasn't my intention, but I've been trying to move forward since."

The NFL reinstated Peterson from suspension in April, but he skipped last week's OTAs amid reports he was unhappy with his situation as he griped about his contract and the team on Twitter.

But on Tuesday, Peterson said he was "happy" to be with the Vikings and ready to get started.

"I would have loved to be out with the guys playing (last season), but that wasn't the case," he said. "After a year of recovery, my body feels good, feels fresh. My body was able to recover, just rest, physically and mentally as well."

Peterson's name was linked to trade rumors throughout the offseason, even as Vikings officials said they wanted him to remain with the team. But Vikings coach Mike Zimmer said Tuesday there were no trade talks involving the 2012 NFL MVP.

Zimmer said the players and coaches welcomed Peterson back because they "know what kind of a person and what kind of a player he is."

"I will help him in any possible way I can and I know the players in this locker room will help him in any possible way they can," Zimmer said. "He's a Minnesota Viking. He's one of our guys. He's going to be wearing the purple with us and fighting with us and sweating with us."

It was a change in tone from Zimmer's comments last week, when the coach said Peterson had two choices: play for the Vikings or not play at all this season.

Peterson, who admitted Tuesday that he contemplated retirement, said last week he wanted security the with team and that his decision not to attend workouts was strictly business.

He has three years and $44.25 million left on his current deal. However, none of that money is guaranteed. Peterson is set to make a base salary of $12.75 million in 2015, $14.75 million in 2016 and $16.75 million in 2017.

Peterson's absence from the Vikings began when he was placed on the commissioner's exempt list on Sept. 17. After reaching a plea agreement in his case, he was suspended by NFL Commissioner Roger Goodell in November for violating the league's personal conduct policy.

The suspension was based on a more stringent player conduct policy that was agreed upon after the actions that led to the charges against Peterson.

Arguing that the new policy shouldn't be retroactively applied in Peterson's case, the NFL Players Association filed an appeal on behalf of the running back, which was denied by league-appointed arbitrator Harold Henderson in December.

The union then filed a federal lawsuit, leading to a ruling by U.S. District Judge David S. Doty in February that ordered the NFL to change its decision in Peterson's case.

The NFL appealed the decision to the Eighth Circuit Court of Appeals and returned Peterson to the commissioner's exempt list before reinstating him in April.

And last month, the NFL Players Association filed a motion to have the NFL and Goodell held in contempt of court over their handling of the suspension and for ignoring Doty's decision.

Amid all of this, Peterson said he didn't address the team as a whole upon his return Tuesday.

"There's a lot of faces I don't know, but the guys who know me, they addressed me and I addressed them. It was family," he said. "It was different because I haven't been in the building for a long time but the love was there. Everyone who greeted me or I greeted it was with a hug, rubbing on the head or cracking jokes. It was pretty smooth, actually."