EAGAN, Minn. – The first day of Verizon Vikings Training Camp is underway.

A total of 37 Vikings rookies and select veteran players reported to Twin Cities Orthopedics Performance Center on Monday afternoon and took to the field Tuesday for the team's morning walk-through.

Vikings Head Coach Mike Zimmer addressed Twin Cities media members following the session and said he's excited to be back in teaching mode.

"It's good for us to get the rookies back in here," Zimmer said. "It's a good chance for us to slow the pace down, teach, give them an opportunity to refresh what we did in the spring. We finished up good in the spring, and it's just part of the journey that we're starting up here this morning, we'll get the vets in here Thursday and we'll go to work."

Zimmer acknowledged that the voluntary Organized Team Activity practices and minicamp that occurred this spring move quickly, and it's not realistic for young players to have absorbed 100 percent of what was put on their plate during that time.

These three days of practices before Friday's first full-team practice will give rookies another chance to get up to speed on play calls, alignments and so on.

"These guys won't recall everything," Zimmer said. "But once we get in the playbook, it will get to the point where they're going, 'Oh yeah, I remember we did that in the spring, and this is how we did it.' "

Here are four other topics Zimmer addressed during his podium session:

1. Group effort on roster management

One of the players present at Tuesday's walk-through was new Vikings offensive lineman Tiano Pupungatoa, who had **just signed with Minnesota on Monday** after the release of running back Roc Thomas.

Zimmer was asked how involved he is in "churning the bottom of the roster" and keeping tabs on some of the turnover that may occur during this time of the year.

He credited Vikings General Manager Rick Spielman, Vice President of Player Personnel/Assistant General Manager George Paton and Director of Pro Scouting Ryan Monnens for not leaving any stone unturned.

"They do a really good job of keeping everything up to date," Zimmer said. "I talk to them about our guys and where we need to get more improvement, and then they'll bring me guys, 'Maybe this is a guy we should look at,' and we kind of go from there.

"They have a list of guys who are available, talk about the waiver wire every day – they go through the waiver wire, I'll go through the waiver wire," he continued. "[There could be] a guy I might know or might have looked at before or something like that, and then we get together and we talk about those things."

2. Emphasis for young running backs

The Vikings have two running backs currently at camp: 2019 third-round selection Alexander Mattison and Mike Boone, who joined the team as an undrafted free agent last year.

Zimmer said the biggest thing for Boone and Mattison during training camp is to improve in the pass protection part of the game.

"The pass routes that they have to run, making sure they're precise on those," Zimmer said. "Carrying a ball, for those guys it's pretty natural, but the other part is where they've gotta get in a certain route and it's a read route, or they've got to go out instead of in, or they have to block this linebacker or that linebacker, whichever one comes, or a pass-off with the offensive line. Those things are all things that take that most time for running backs."

3. Rookies then versus now

Zimmer has been in the NFL a long time and has seen the league change in various ways.

What are the biggest differences he sees in rookies and young players today versus those he worked with in Dallas in 1994?

"They don't have to go through two-a-days in full pads right off the get-go every single day," Zimmer reflected, referencing changes in the Collective Bargaining Agreement that have altered the look of NFL training camps.

"The biggest thing I do think has changed quite a bit since I first started, [is] guys would eat [fast food] and all that stuff," Zimmer pointed out. "These guys are pretty careful about what they put in their bodies and the nutrition aspect of things. The weightlifting, all the different things that they do now is, I think, much more sophisticated – the sleep, all the recovery things that they do is much more sophisticated."

4. A baseball analogy for defensive change-ups

The Vikings offensive coaching staff looks quite a bit different now than it did a year ago.

Minnesota's defensive staff and system, however, has remained mainly intact since Zimmer took the helm in 2014. So, just how much change can we expect from the Vikings defensively in 2019?

"In baseball terms, I would probably say, you know, 'Fastball, fastball, change-up. Fastball, fastball, throw a slider in there once in a while,' " Zimmer said. "Just give the offense a couple different looks that they have to work on and things like that."