EAGAN, Minn. — Undrafted running back Mike Boone sauntered off the field last week at TCO Performance Center with backfield mates Roc Thomas and Mack Brown by his side.

The three players looked like lifelong friends, joking as they retreated to the Vikings’ locker room following another long day of training camp. You never would have known that they’re actually battling for the same spot on the active roster.

“Those are my boys,” Boone said, emphasizing that there’s no bad blood between the trio. “You don’t let that stuff that get in the way of things off the field. We come out here and compete and leave that between the lines. As soon as we’re done, it’s all good between us.”

Nonetheless, with Dalvin Cook penciled in as the starter in the backfield, and backup Latavius Murray pushing for extra reps after a strong performance in the preseason opener Saturday against the Denver Broncos, only the third running back spot is still up for grabs.

After his performance over the weekend, Thomas is the leader in the clubhouse. He looked dynamic in both the run and pass game in his preseason debut, scoring a pair of touchdowns, including an electrifying 78-yard scamper on a screen pass out of the backfield.

That said, Boone and Brown also impressed coach Mike Zimmer with their play; Boone carried 12 times for 22 yards, and Brown carried 11 times for 34 yards.

“All three of them had some very, very good runs,” Zimmer said. “They showed some explosiveness. I was pleased with those guys. Hopefully we can continue to work with them and see where it leads.”

Whoever wins the job likely will see most of his reps as a change-of-pace back, a spot occupied last season by Jerick McKinnon, who is now with the San Francisco 49ers.

Whoever loses the job likely will be looking for work elsewhere.

“It’s a great vibe in the room,” Thomas said. “We don’t even think of it like one of us has to go or two of us has to go. We try to help each other get better. That other stuff will play itself out.”

All three are glad to be working with running backs coach Kennedy Polamalu, who is recognized across the league for his vast knowledge of the position.

“He’s one of the best in the league, so we’re learning a lot from him.” Brown said. “Before, I kind of just ran with the ball. Now I know where the fits are and things like that. I’ve become a better player overall. We all have.”

Eventually, somebody will run away from the pack and secure the job behind Cook and Murray. As of right now, though, the competition is far from complete.

“It elevates our game going against each other,” Boone said. “We have to come out here and compete no matter what. We have a lot of great athletes, so all of us know when we get in, we have to make a play. No days off. No plays off.”