David Johnson has been a revelation for the Arizona Cardinals, for all of us.

Johnson was a relatively unheralded 86th-overall pick out of Northern Iowa in this year's draft. He now has six touchdowns on the year, tied for second-most in the NFL. For a little context into the blistering start he's had, consider: he's the first rookie since the legendary Gale Sayers in 1965 with multiple rushing touchdowns (three), multiple receiving touchdowns (two) and a return touchdown over his first five games as a pro.

I shouldn't be surprised. The 6'1, 224-pound running back set all kinds of records at Northern Iowa, rushing for 4,682 yards and 49 touchdowns in four seasons there, while adding 141 catches for 1,734 yards and 14 touchdowns through the air.

He was an absurdly productive player in college. Then, he blew the doors off his combine performance, running a 4.50 40-yard dash while adding a 41.5-inch vertical leap and a 10'7 broad jump while showing some agility as well, with a 6.87 three-cone run. The tools and stats were all there. And yet, I'm still surprised at how good he's been already.

Running back

My first impression of Johnson's game was that while he obviously looks like an NFL back and blew everyone away with his athleticism at the combine, he was a bit of a stiff, upright (and tall) runner who would struggle without good blocking in front of him. His first NFL rushing touchdown had me backing off of my initial thoughts, though, because of his smooth, easy speed. It actually reminded me a little bit of Matt Forte, where you don't really think he's even running very hard, but blows by people.

Watch as he reads his blocks. Sherrick McManis (No. 27, the defender in the slot) goes to the outside of the pulling guard's block, which is Johnson's read to cut it inside -- and that leaves Johnson with one defender to beat, essentially. The safety to that side sees where the play is going, slips briefly, then tracks the run outside. That's when Johnson absolutely destroys the oncoming safety's pursuit angle on his way to the touchdown. A subtle head-fake toward the middle of the field is all it took.

While that run was impressive, Johnson's footwork has really been what's made me sit up in my chair and take notice.

For a taller guy, leverage and quickness can sometimes be an issue at the NFL level, and Johnson's ability to chop his feet and keep his momentum going forward has been pretty damn impressive.

Check out these two runs. Nothing flashy, but this is what you want from a guy that, while he's primarily a pass-catching threat, will still get some short-yardage stuff and between-the-tackles runs.

He sticks with runs and shows a combination of patience, balance and power. He keeps his legs churning while protecting the football and pin-balling off defenders.

His running back chops aside, I think one of the main things the Cardinals saw in Johnson was his receiving acumen.

Receiver

Johnson has had a few drops -- including one that would've gotten him his seventh touchdown on the year, absurdly enough -- but overall has been a very dependable and versatile receiver. The Cards have used him in just about every fashion imaginable.

The dangerous upfield wheel route. On this play, Raiders linebacker Ben Heeney appears to read a flat route out toward the sideline, and takes a bad angle of pursuit. That bad pursuit angle thing shows up a lot with Johnson, by the way. Dude is just faster than he looks.

This is what happens when you try to put a linebacker on him. It's no contest, really.

Again, with Johnson aligned on the left side of the formation, he draws coverage from the middle linebacker, David Hawthorne, who starts out to the right, reading the fake sweep from John Brown. At this point, the defense is screwed in terms of giving up a first down. Johnson has the angle, has two or three steps on the linebacker in coverage, and it's an easy pitch and catch from Palmer.

However, again, I couldn't believe these pursuit angles! He busts it upfield for seven, like it was nothing.

Just out here killing pursuit angles.

I loved this little seam route he ran against the Rams, as well. Not sure what safety T.J. McDonald was waiting for here, but once Johnson had a step on him, it was done.

The cool thing about how the Cardinals have used Johnson is that he's not just a route-runner from the backfield. They feel fine lining him up outside as a receiver running receiver routes. That versatility allows Bruce Arians to do so much with formations, and with personnel.

One more: remember how I said his feet are better than I thought? Look at him finish on this catch.

Impressive.

Returner

One final piece to the puzzle that makes Johnson so valuable thus far for the Cardinals is that he's featured into the return game, as well. He took this one to the house in Week 2, and again, his easy speed just shows up.

It's obviously early, but the returns thus far have been very promising for David Johnson. He's a backup/situational player in the Cardinals' scheme behind a very strong performance by veteran Chris Johnson thus far -- but he has been making the most of his opportunities. The younger Johnson has turned nine catches and 18 carries into five offensive touchdowns, and that return score is just the cherry on top.

Look for the Cardinals to increase his usage as the season goes on though, and while defenders might start figuring out that you have to give him a little wider berth in pursuit, he's still bound to be a very productive player in that Arians' system, both as a receiver and runner.

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SB Nation presents: You have to see this touchdown to believe it