See more of the story

The Vikings don't want to shovel dirt on this fire.

Minutes after Stefon Diggs' fingertip grab for a 25-yard touchdown against Green Bay — capped by his pantomimed "digging" celebration — he let his emotions get the better of him. As three defenders piled onto teammate Cordarrelle Patterson after a short run, Diggs felt they lingered too long.

So he rushed onto the field, helmet in hand, to help up Patterson. In the end, Diggs hurt his team with a 15-yard unsportsmanlike-conduct penalty that stalled a fourth-quarter drive.

"That was dumb," Diggs said. "Moving forward, that will never happen again. It should've never happened in the first place."

In that instance, Diggs stepped over the line and it cost him $12,154 in an NFL fine. Diggs certainly would like to keep his money, but the Vikings will take the passion that led to the penalty.

It's just one example of an unrelenting competitiveness that teammates and coaches say is a core reason for why Diggs, a 2015 fifth-round pick, has become the NFL's leading receiver with 285 yards through two weeks and two different starting quarterbacks — all at just 22 years old.

He was held out of practice Friday with a groin injury; however he's expected to play Sunday against the Panthers.

Vikings defenders say they could see his drive from the beginning, whether he was beating them with impressive grabs on the scout team or not. When he'd fail, "he'd get mad at us when you cover him too good," cornerback Captain Munnerlyn said. "You're like, 'What's going on?' and he'd just say, 'I got to get open.' "

So there was little surprise when Diggs thrived after getting his chance as a rookie. After he was inactive for three weeks, he started in Week 4 against the eventual Super Bowl champion Denver Broncos and went on to become the first rookie to surpass 85 receiving yards in each of his first four games.

"You can see it early," receivers coach George Stewart said. "If a puppy bites when he's young, when he gets to be big he's going to really bite you. He had some bite in him as a young puppy. You saw what he did when he came in last year and started to play. It wasn't a mistake he played well.

"I like his competitive fire."

Diggs said he's motivated first by his family, setting an example for his two younger brothers, Darez and Trevon, whom he's looked after since his father, Aron, passed away when he was 14. That's why he stayed close to home for college at the University of Maryland despite fielding offers from top programs across the country. But don't let the "fifth-round draft pick" in his Twitter profile slip past you.

His talent starts at the bottom with his feet, which lead to crisp routes and a feeling as if he's always open. Diggs has worked to build up the rest while adhering to daily footwork drills designed to maintain his quick step. Vikings coaches sent Diggs into the offseason with a goal to add muscle to his frame.

Coaches have met him halfway this season by moving him around the formation, whether at flanker or in the slot, to give him the best matchups against cornerbacks.

At 6 feet and bulked up 10 pounds from his listed 191, he's already ascending in his second season.

"He has been extremely competitive," coach Mike Zimmer said.

One example came in August, when Diggs showed he's not backing down from a $51 million man.

During a goal-line drill in training camp, tensions rose when Diggs and Harrison Smith, one of the league's highest-paid safeties after signing a five-year extension this summer, had to be separated by linebacker Chad Greenway, who cautioned Diggs with a "you don't want none of this."

"You could just sense his attitude," Greenway said. "It's not like he was disrespectful. It was just 'I'm here to compete' sort of mentality, which is great. There's a difference than just being disrespectful, just being a young punk. But if you're really there to compete, taking it personal, then that's a good thing."

Smith senses the same from Diggs, who takes any failure as an attack on his ability.

"We take this game personally," Smith said. "That's why he's so good, because he takes everything personal. So I think he'll probably always carry that with him."