Peterson, who will be out for the Cardinals' first six games of the 2019 campaign for violating the league's performance-enhancing drug policy, wasn't expected until next week's mandatory three-day minicamp. He had previously missed the first two weeks of voluntary drills.
"We've been in communication throughout the offseason," Cardinals coach Kliff Kingsbury said. "It was great to have him back. He's a great teammate, a great player, and he brought some good juice."
Kingsbury said Peterson's absences were planned, as he was taking care of his young daughter. Peterson said he will attend Tuesday's and Wednesday's sessions.
Speaking to reporters after the workout, Peterson was asked what led to his suspension, the first of his career.
"I failed a PED test, and I'm looking forward to coming back on Oct. 14. I'm very, very deeply sad and sorry that my name is associated with this and also that I'm letting my brothers down," he said. "It's behind us now, and I'm looking forward to coming back against the New York Giants [on Oct. 20]."
One highlight of Peterson's outing was an interception off rookie quarterback Kyler Murray.
"It was a welcome-back gift; he gift-wrapped it for me," Peterson said.