The reigning NFL MVP took to Twitter to say he felt like he'd "been kicked in the stomach" and called Harvin "the best all-around player I ever seen or you'll ever see."
With the Vikings set to play the Seahawks on Sunday -- and Harvin possibly ready to make his season debut after missing the first 10 weeks with a hip injury -- Peterson said he's glad to know Harvin is happy in Seattle.
"Obviously, we wanted him here," Peterson said. "He felt some other type of way. He's happy, he's able to play the game he loves and we're moving forward. This is a business. It happens."
Before Harvin sprained his ankle against the Seahawks last November, he was in the MVP conversation alongside Peterson, having caught 62 passes in the Vikings' first nine games and returned a kickoff 105 yards for a touchdown. But Harvin reportedly clashed with coach Leslie Frazier before the Vikings put him on injured reserve in December, and with concerns looming over both his durability and his compatibility with the rest of the team, the Vikings traded Harvin for three draft picks just as he was entering the final year of his rookie contract.
"If you'd told me when we drafted him [in 2009] that he would be playing for Seattle right now, I would have looked at you crazy," Peterson said. "Like I've said before, he's the best player I've ever played with. We have the same mindset. There's not too many guys that play with that mindset to win -- Brett Favre, Drew Brees, Ray Lewis -- he has that type of mindset. ... You never had to get on him about practice. He came out and practiced hard, pretty much like it was a game."
The day Harvin got injured in Seattle, cameras also caught him screaming at Frazier on the sideline, and just before Harvin was traded, reports surfaced that the Vikings wanted to move on partially because of the receiver's criticism of quarterback Christian Ponder.
But Ponder, who has said before that his relationship with Harvin was fine, downplayed the idea of a rift again on Wednesday.
"I haven't talked to him [since he was traded]. I'm sure I'll talk to him on Sunday," Ponder said. "Things, I thought, were fine between us. I remember him saying the same thing to the media when he addressed it. I don't think there's really much of a story there."
When asked why things didn't work out for Harvin in Minnesota, Frazier said, "Lots of reasons. Lots of reasons. Lots of details to that story. But I hope he does well. I wish him nothing but the best."
Ponder, who dislocated his left shoulder in the Vikings' win over the Washington Redskins on Nov. 7, said he is practicing with a harness on his shoulder and plans to wear one Sunday.
Frazier has yet to officially name Ponder the starter for the Seahawks game, but Ponder said again Thursday he expects to play.
"I threw it around a lot more than I expected to yesterday," he said. "Practiced pretty much the whole practice. And I thought it went well."