Steve Serby

Steve Serby

NFL

RG3’s Redskins face Kelly’s hurry-up Eagles in battle of unknowns

Chip Kelly shows up tomorrow night at FedEx Field and the NFL braces for a brave new world where there is much more to fear than fear itself.

Hail to a matchup where the long-awaited return of RG3 from ACL surgery and the internal political football game over his progress is trumped by a rookie head coach brazen enough to leave his Nike cocoon at Oregon and attempt to rattle traditional cages with a new-age offense designed to wear defenses to a frazzle and leave coordinators confounded and shellshocked.

This is the moment when the read option confronts the speed option.

There had been other lethal weapons with golden arms and winged feet — Randall Cunningham and Michael Vick, for example — before Robert Griffin III showed up last season with all that charisma and immediately began electrifying everyone and everything in and around the White House and even overshadowed fellow rookie Andrew Luck and Colin Kaepernick until the end.

Everything was hog heaven, until Mike Shanahan and Dr. James Andrews made the egregious decision that trying to win a playoff game at home against the Seahawks was of more importance than the health and well-being of their one-legged franchise quarterback.

Now we watch and wait and root that RG3 finds the right balance of fearlessness and smarts when the read-option demands he uses his legs again.

This by itself would be compelling theater, but the arrival of the mad scientist new coach of the Eagles with his test-tube offense already has had more far-reaching consequences because it has inspired laboratories all across the league to keep the lights on.

No one is certain whether Kelly will be little more than a meteor flashing across the sky over the Linc, because even the great Nick Saban was driven back to college after two unfulfilling years with the Dolphins. But if Kelly is all-in, then the NFL is in for a rude awakening. This is a bright, driven football gym rat who doesn’t seem likely to get all warm and fuzzy over “Rocky” or the Vince Papale tale. He’s here to win football games, and win them his way, and they better get him now, because when he recruits players who fit his system better, beware.

“I think you have to be ready for speed of play,” Mouse Davis said over the phone. “It’s a different speed level, no question about it.”

Back in the mid-1970s, Davis was an innovative coach who defied convention with his run-and-shoot offense — quarterback under center, four wide receivers. The NFL scoffed at it.

“Everyone in the NFL said you can’t run that stuff,” Davis said.

Then virtually everyone in the NFL embraced that stuff.

“We were always gonna be right at the snap of the ball,” Davis told The Post. “No matter what you do, you’re gonna be wrong. We’re gonna read what you do at the snap of the ball, and whatever you do, we’re gonna do something that will defeat that, because we’re gonna be able to vary our our route or routes to what you do on defense. We’re gonna be able to make the right decisions to have success.”

Eyebrows were raised when Davis’ Portland State team nuked Delaware State, 105-0, in 1980.

“They had three kids on that team that later played in the NFL,” Davis said. “They were a badly prepared team. We had three quarterbacks who threw for over 250 yards. It isn’t like you’re trying to pour it on. We only had three quarterbacks, what are you gonna do?”

Jim Kelly would operate the run-and-shoot in the mid-1980s for the USFL Houston Gamblers, and Davis brought it to the Lions as Wayne Fontes’ offensive assistant. Davis once described it as a two-minute drill … the entire game.

“Football coaches are the greatest copiers in the world,” Davis said. “Whatever works, they want to use it.”

The recent NFL memo warning defensive players against faking injuries figures to be put to the test against the crazed Michael Vick-LeSean McCoy-DeSean Jackson Eagles, who will feast on anyone and everyone sucking wind. The nature of the Kelly attack demands the Eagles defense is in top condition to practice against it.

“From the very beginning, we have talked in the Eagles locker room and our meetings rooms defensively about, it’s not the Philadelphia Eagles offense that is no-‑huddle and up‑-tempo, “ defensive coordinator Billy Davis said. “It’s our whole team. Our defense is just as ready for us to be a three‑-and‑-out or a three-‑and-‑in. If it’s half a sip of Gatorade and you have to go back on the field, so be it.”

Though both Vick and RG3 must be wary of predators delivering gray-area hits once they hand the ball off, McCoy is relishing a bigger role, considering Kelly’s run-pass ratio at Oregon was 65-35.

“I think he’s a bright enough offensive mind that he can vary his attack depending upon what his players can do,” Davis said.

Kelly contends those statistics can be misleading.

“There were a couple games we scored so fast, it caught me by surprise,” he said. “We’re up 43-‑7 with 11 minutes to go in the second quarter. You’re like, ‘Holy smokes.’ ”

Puff, Daddy.