EAGAN, Minn. – It doesn't seem that long ago that Alexander Mattison was playing with Stefon Diggs in Madden.

Now, the star of the Minneapolis Miracle casually jokes around with Mattison in the Vikings locker room. It's taken a little getting used to for the rookie running back who turned 21 today.

"At first it was a little surreal, but now it's getting a little more comfortable," Mattison said with a smile following a Vikings minicamp practice last week. "Diggs, he'll joke with me about 'swag for the day' and stuff like that, and [Adam] Thielen, he's great at giving you bits of advice here and there.

"These are guys I watched on TV and played with [in video games] when I was in college, and now that they're my teammates, it was surreal at first, but now it's kind of setting in, and I'm just trying to work every day to get better," Mattison continued.

Minnesota snagged Mattison with the 102nd spot in the 2019 NFL Draft. The Boise State standout had caught the eye of Vikings coaching staff, including running backs coach Kennedy Polamalu.

Polamalu told Vikings.com's Mike Wobschall during a recent interview that Mattison fit everything the team was looking for in the position: an ability to catch the ball out of the backfield, a physical runner, stamina.

"He gets stronger and stronger the more touches he has. He can drop his hips. He can lower his pads. And he's smart," Polamalu said. "And then off the field, all the boxes are checked. He's a good young man, he's a good teammate, accountable, and he's going to be a young man that I think will make an impact.

Added Polamalu: "He's no surprise because that's what we saw on film, and he's added more by his character."

Asked about learning from Polamalu, Mattison said it's been an adjustment – but a positive one.

He recalled the few meetings with Polamalu and feeling at first that he wouldn't be able to keep up and digest all of the information. With time, however, the teaching style has instead been a motivator for Mattison to study even more on his own.

"He moves very fast, but he does it for a reason. He wants us to be able to play fast," Mattison said. "I like it. At first, it was kind of like, 'Oh, I missed that. I don't know half of the stuff that he just went over.' So I have to go back and look at it. But that's part of the responsibility upon us, to go back and review things on our own and to catch things that he's saying at a fast pace because the game happens so fast.

"His coaching style correlates with the way the game is played," Mattison continued. "He's definitely hard on us, but he shows us a lot of love, too. I think he has the perfect blend and mix of style of coach that you want."

While learning a different system has been challenging, it helps that he isn't doing it alone. The entire Minnesota offense is operating under the new leadership of Offensive Coordinator Kevin Stefanski and Assistant Head Coach/Offensive Advisor Gary Kubiak, and Mattison described it as a group effort in the classroom.

From what he's seen of the 2019 Vikings offense so far, Mattison is excited.

"I love how involved running backs are and how many opportunities we have to get the ball in our hands to make plays. I definitely think that a good rotation will make sure that we stay fresh, and I just think this offense is looking really good," said Mattison, who pointed out that there are some similarities to Boise State's offense.

"It's not completely new to me," Mattison said. "Just a lot of different, new terminology, and it's way more vast than it was in college."

Mattison called the Vikings running back room "a brotherhood." He values the opportunity to work with Dalvin Cook, Ameer Abdullah, fullback C.J. Ham and the undrafted free agents from last year's class, Roc Thomas and Mike Boone, and this year (fullback Khari Blasingame).

He explained that the group is an unselfish one.

"It's never a hostile environment," Mattison said. "It's all about making sure that the whole group is doing well and the whole group is able to go out there and perform at a high level."

Cook, entering his third season in Purple, and Abdullah, who joined the Vikings in November after being released by the Lions, have been especially helpful for the younger back.

"Hand on the shoulder, take me under their wings and just letting me know what I could have done [differently in a certain situation]," Mattison said of their similar mentoring style. "There's a lot of different ways they're helping me out. Ameer, he's shiftier, so he helped me out in thinking about choice routes and things like that. Dalvin, [he's been helping] me with my outside zone, footwork, timing and everything like that.

"Those guys do a great job with looking out for me and trying to make sure that I'm taking the right steps," he added.

Mattison is soaking up anything and everything he can, and it isn't just from the offensive side of the ball.

He's appreciative of teammates alongside him – some of them quite literally, in the case of Eric Kendricks and Eric Wilson. The pair of Erics have lockers that flank Mattison's. He said the linebackers are quick to help him out.

"They both give me great advice on how to take care of my body and things like that," Mattison said. "I appreciate those guys and look forward to continuing to grow those relationships with different players on the team."

With Vikings minicamp now in the rearview mirror, Mattison is enjoying some downtime with family and continuing his workouts to ensure he's back in Minnesota next month, ready to get back at it.

The rookie's main goal heading into his first NFL training camp is broad but important: improve in some aspect every single day.

"I [just plan to] take it day-by-day and have the goal in mind to get better every day," Mattison said. "Any mistakes that I have, correct them and just continue to get better and learn. Everything else will fall into place."