In addition to RB Adrian Peterson, who was place on the active PUP list on Friday, coach Leslie Frazier announced that two other players, WR Stephen Burton and TE Mickey Shuler, were injured and not yet able to practice at training camp.

Frazier said that Shuler has a heel injury he suffered a couple weeks ago and he would be performing some activities off to the side of practice until he is ready to return.

“He is going to be day-to-day as we try to determine when is the right time to put him back out there with his teammates. We don’t think it’s a serious injury but we have to do some things with it with our trainer to determine just how serious that injury is. The x-rays that we took and the MRI are all negative.”

Burton jammed his toe a week or so ago and has been placed on the active NFI (non-football injury) with Shuler. They can be activated at any time.

“In both Mickey and Stephen’s case, we don’t think these are going to be long-term absences. We think that they are going to be out here in a short period of time. But we have to go through this period, where we can evaluate them for ourselves and then make a determination.”

Following afternoon practice on Friday, Peterson spoke to the media about the decision to place him on the active PUP list.

"It is tough (to watch practice), but it is what it is,” said Peterson. “I just have to make the best of what I am doing on the side and whenever they release me I will be ready to roll.”

Follow Vikings reporter Joe Oberle on Twitter: @CBSportsNFLMIN.