When the Minnesota Vikings arrived at training camp, it was unclear how the post-Adrian Peterson backfield would shape up. Now as the Vikings head into their third preseason game, rookie Dalvin Cook has put himself in position to be the team's No. 1 running back.

His emergence to the top of the depth chart, according to quarterback Sam Bradford, can be attributed to the rookie's ability to pick up the Vikings' offense quickly.

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"When you're young, you're thinking a lot, there's a lot going on, sometimes the speed gets to you, but for him, it's been really seamless," Bradford said. "We put a play in, we put a protection in, we put a scheme in, and it's like he's got it."

Cook has received plenty of opportunity to show his skills during the preseason. In two games, he has totaled 12 rushes for 53 yards and five catches for 50 yards while playing exclusively with the starters.

At Florida State, Cook set the university's all-time rushing record and was a weapon in the passing game, but he was rarely asked to block. Bradford said he's been impressed how fast the former Seminole has picked up pass protection.

"He's really good in protection, which I think is key for him to be able to be out there first, second, and third down," Bradford said. "I think that has been what's allowed him to step out there and be successful."

Head coach Mike Zimmer credits Cook's progress with his effort away from the practice field.

"He works hard and studies," Zimmer said. I think [running back's coach Kennedy Polamalu] is doing a nice job with him. He hasn't made very many mistakes and when he does, he doesn't typically repeat it."

The Vikings expect to have free-agent signee Latavius Murray in the backfield for the first time this preseason when they face the San Francisco 49ers on Sunday. Whether he or Cook takes the opening series could be an indication of how the Vikings will divvy up snaps in the regular season.