The NFL's leading rusher in 2015 has missed the team's first two practices, but Zimmer doesn't expect Peterson's injury to be long-lasting.
Peterson took the Vikings' conditioning test Friday, a day after the rest of the roster did, and worked on the side with the team's athletic training staff for a second straight day Saturday.
On Saturday morning, Peterson said he would be fine, and Zimmer said the light workload was more out of caution than anything else.
"He can do things; he just can't turn it all the way loose," Zimmer said. "We're just being careful."
As the Vikings ease Peterson into action, they've had a chance to take a longer look at Jerick McKinnon, who posted 673 yards from scrimmage as a rookie and helped jump-start the team's offense late last season as a runner and a receiver.
McKinnon, who posted 444 yards on 73 touches in 2015, lined up at wide receiver Saturday. He caught a deep ball in stride from backup quarterback Shaun Hill and high-fived fans as he strolled into the end zone.
"It's good we get to see some of these young backs. But [Peterson will] be out here fairly soon, I think," Zimmer said.
The coach also said wide receiver Cordarrelle Patterson, who injured his left shoulder while making a diving catch Friday, would be back on the field in a few days.