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.
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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.