MANKATO, Minn. —The Vikings have six running backs present at training camp in Dalvin Cook, Jerick McKinnon, Latavius Murray, Bishop Sankey, Terrell Newby and C.J. Ham, who has also taken reps at fullback.

Murray was declared to the Active/Physically Unable to Perform List before the first practice in Mankato.

Vikings Head Coach Mike Zimmer was asked for an update on if the veteran will be able to participate by the end of camp.

"I don't know," Zimmer said. "He hasn't gotten the OK yet. He is a smart guy, but he needs to get out there."

When healthy, the Vikings are confident that the team can find a balance in the three-headed backfield of Cook, Murray and McKinnon, who all have different strengths.

"I think it gives defenses a different look when you have a different style of back coming in. It's a lot of wear and tear on guys as well when they've got to do protection, third downs, all those things," Zimmer said. "There's a lot of backs that do it, it's just based on the player and the team."

Cook has seen a majority of the reps with the first team so far, and Zimmer said he has done good in pass-protection.

McKinnon was injured during the Vikings first full team practice but was back in pads with his team participating in practice on Sunday.

During McKinnon's absence, Sankey, a former Titans 2014 second-round draft , has seen a few extra reps.

"He's done a nice job seeing the cuts," Zimmer said. "I kind of liked him when he was coming out of the University of Washington. He's done a nice job, we're trying to run some of these one-cut runs. I think he's done a good job with seeing that and being able to cut back. He's done a good job. He's going to have to work in protections."

Here are four other topics Zimmer discussed on Monday:

1. Roster cuts

During the offseason the NFL Owners voted to make a change in procedures for roster cuts during training camp.

In the past, teams cut the roster from 90 players to 75 after the third preseason game and then cut from 75 players to 53 players after the fourth preseason game.

This season there will only be one roster cut from 90 players to 53 players after the fourth preseason game, leaving more opportunity for players to prove their worth.

"I like it," Zimmer said. "I think it gives a lot of other guys more chances to be evaluated with that fourth preseason game. It will be harder on Rick [Spielman] on the waivers when everything happens, but it's good for the players. They get a chance to not just show in a couple of games, but four."

2. Assessing Jayon Kearse in year two

The Vikings found a wild card during the end of the 2016 draft in former Clemson Tigers safety Jayron Kearse. Kearse has rare size for a safety at 6-foot-4 and showed the ability to be effective on special teams last season. Zimmer is confident in Kearse's athletic ability, but wants Kearse to take his talents to the next level in the preseason games.

"The biggest thing he's got to do is be able to drop his hips in space and be able to make open field tackles," Zimmer. "That will be his biggest struggle. I think he knows what to do now. He's a good athlete, good range, good size, physical. That will be the biggest test for him. Those won't show up probably until the preseason games. You can kind of see a little bit on tape, but if the safeties miss tackles that's not a good deal."

3. Hunter's transition to starter

Vikings third-year defensive end Danielle Hunter begins his first season as a starter on the defensive line.

Hunter has 18.5 sacks in a limited role in his first two seasons learning behind veteran Brian Robison. While Hunter has shown the ability to be an elite pass rusher, Zimmer looks for him to improve in another area.

"Probably playing the run," Zimmer said. When he's in the 6-technique, that'll be the biggest struggle for him."

4. Tuesday's day off

The Vikings will have their first day off since the start of 2017 Verizon Vikings Training Camp on Tuesday.

Zimmer commented on the benefits of a rest day for his players at this point in camp.

"I think it'll be good for the players," Zimmer said. "They banged pretty good yesterday and the day before. I think it'll be good for them to get the day off. For the rookies, they've gone seven or eight days straight. Some of those guys are sort of dragging a little bit. It'll be good for them."