GLENDALE, Ariz. -- Ask the Arizona Cardinals how running back David Johnson looks at training camp, and you'd think you'd just asked somebody about their buried treasure.

"Man ... people don't know," tight end Darren Fells said. "But they're going to know."

"I'm afraid to say it," coach Bruce Arians said," because then he'll get hurt."

"I don't even want to talk about what I've seen from David Johnson, because I don't want to jinx it," general manager Steve Keim said. "It's scary."

Johnson was plenty scary last year, when he had 13 touchdowns as a rookie -- eight rushing, four receiving and one kick return for good measure. He averaged 4.6 yards per carry, and over his final seven games -- five in the regular season and two in the playoffs -- he averaged 135 yards from scrimmage per game.

But those aren't the only reasons for the rattlesnake-caliber buzz swirling around Johnson in the Arizona desert. Something about the Cardinals' 2015 third-round pick feels even more exciting this year.

"He's got rare and unusual skills I've never seen in a back, where he's got an erect running style, yet at the same time he has tremendous lower flexibility and lateral quickness," Keim said. "So that's a weird combination, because usually those taller, upright guys are kind of straight-legged and stiff. This guy's got an unusual knack of being able to pick and slide and do some things laterally. And then his receiving and ball skills are second to none.

"I mean, probably the best receiving back I've seen."

Like ... ever?

"A lot of people have compared him to Marshall Faulk, and our coaches had Marshall Faulk in Indy," Keim said. "I think he's very similar in some ways athletically and in terms of ball-catching skills to Marshall."

Johnson had 14 total touchdowns as a rookie (postseason included), proving to be an effective end zone threat. EPA/Erik S. Lesser

Pretty lofty stuff. Fortunately, it's not the stuff that seems to be filtering its way to Johnson's own ears. A couple of weeks ago, Johnson stopped for an interview after a tough practice. He'd missed a blitz pickup and spent the rest of the practice with Arians screaming at him about it.

"Yeah, I just got yelled at," Johnson said. "Just so mad at myself for doing it, because I thought I was getting better and learning a lot more, and I think it was just one of those things I might have just overlooked and just assumed. I always have to be ready for that."

Good to keep 'em humble, obviously, and the way Johnson is ripping up practices and preseason games, it's important to make sure he doesn't get too happy about all of his success too quickly. Fortunately for the Cardinals, Johnson seems to be the sort who gets the message when Arians sends it.

"He's a tough coach to play for, because he wants it a certain way," Johnson said. "Every play he makes is set for that certain defense. There's always a route or there's always a play that we should be able to win with against that defense. And usually, most of the time, I was talking to the players, and they say it's the players that mess up. So he's really tough on us, especially me, because he wants Carson Palmer protected. They don't care how good you are. If you can't protect this quarterback, you aren't getting on this field. That was literally the first thing he ever said to me."

"A lot of people have compared him to Marshall Faulk, and our coaches had Marshall Faulk in Indy. I think he's very similar in some ways athletically and in terms of ball-catching skills to Marshall." Cardinals GM Steve Keim on second-year running back David Johnson

So there's the thing that could potentially hold Johnson back. You can't score touchdowns if you can't get on the field. But if he can stay on that field, look out. He's put on five pounds to get up to 229, which should help him run with more power between the tackles. Not even Keim thought the running back would be great at that when he drafted him. Go back a year, and Andre Ellington and Chris Johnson were ahead of Johnson on the depth chart.

"I thought he was a much more gifted pass-catcher than he was a runner," Keim said. "And I see the thing he's probably improved on the most is his inside running skills -- being a taller guy and being able to run behind his pads and finish between the tackles. That was the concern with him being an upright runner -- can he run with his size or is he going to be a finesse perimeter guy? He's shown us the ability to do both, and he's gotten better and better."

So this might be the time for David Johnson. Maybe a year ago, he admits himself, he wouldn't have been ready for the opportunity to be the full-time starter. Missing a blitz pickup assignment in October has far more dire consequences than missing one on Aug. 4, when the defense isn't allowed to hit your quarterback. Maybe right out of Northern Iowa, before he'd figured out how to deploy his unique and considerable skills against hyper-speedy NFL defenses, he'd have had a rough time. Maybe now is the perfect time for David Johnson to happen.

"Me being able to play last year and knowing how the NFL is, the atmosphere of NFL games, it's a lot easier," Johnson said. "I'm a lot more comfortable coming in and getting ready for my second season. And hopefully I can continue to get better and continue to improve."

All this sounds very exciting to the Cardinals, their fans and anyone fortunate enough to have snagged Johnson early last year in a fantasy keeper league.

Just, you know ... don't tell anyone.