And wide receiver Larry Fitzgerald hasn't forgotten.
He still needles general manager Steve Keim, who was the Cardinals' director of college scouting that year, for the team passing on the league's top rusher.
"Oh man, could you imagine?" Fitzgerald said Tuesday. "I always mess with Steve. I'm like, 'Steve, we should've just took him with the fifth pick a couple years back. We could've had a couple Super Bowls right now.'"
It's been eight years of what-ifs for Fitzgerald, who played in Super Bowl XLIII in 2009. It's also been eight years of wondering what life would've been like had Arizona drafted him for Peterson.
"I think about that sometimes," Peterson said Tuesday on a conference call with Arizona media. "My uncle, Ivory Lee Brown, played for the Cardinals for about three or four years, so during that process I was like, 'It'd be pretty cool to go down there and play for the same team my uncle played for.'"
There was an outside chance it could have happened this past spring, when Peterson wanted a trade.
One destination he thought had potential was Arizona, in part because of Fitzgerald. The two talk often, Peterson said. But he didn't say if the two discussed the idea of Peterson playing for the Cardinals. According to USA Today sports, however, Peterson's agent, Ben Dogra, told Peterson on the night of the first round, to "work Larry Fitzgerald" in hopes that Fitzgerald would call team president Michael Bidwill and convince him to trade for Peterson.
"When I was going through that process, of course Arizona was a place that grabbed my attention, especially with the type of season they had last year and the warm weather," Peterson said.
But Peterson didn't want to delve any deeper into this offseason.
"I don't want to get into all that," he said. "At the end of the day, I knew that I would be here in Minnesota when it came down to it."
Like Fitzgerald, Peterson has spent his entire career playing for one team -- Fitzgerald's childhood favorite.
Time does heal wounds but it doesn't also heal memories. Fitzgerald still thinks about what his career could have been like had he played alongside a once-in-a-generation player like Peterson. And Peterson has thought about playing next to the future Hall of Famer.
"I did envision it," Peterson said. "Fitz is a guy I looked up to when I was in high school and has just been an amazing player.
"I've always envisioned having him on my team, even if he came to Minnesota."