First off, it's the "zone-read" and not the "read-option."

Chip Kelly made that point early in his tenure with the Eagles.

"Zone-read is just one guy," Kelly said in November 2013. "You read the defensive end or whomever and keep it. If you're running read-option, you're pulling off of him and then you have a pitch-back."

The Eagles use the zone-read, although not nearly as much, Kelly has insisted, as many believe. It is a play that involves the quarterback in the shotgun, holding the ball in the basket of a running back with two hands and either handing off or keeping based on his read of an unblocked defender.

There are various forms of the zone-read, different defenders who can be unblocked, a range of zone-blocking schemes, and even sometimes options to throw. But it is not the read-option because there isn't another player to potentially pitch the ball to.

It's difficult to say how much the Eagles employ the zone-read because Kelly's quarterbacks, especially since Michael Vick, have so rarely kept the ball and run. The coach contends that there is hardly ever the option to keep.

But the quarterback often carries out the fake, as Sam Bradford did on his first play as an Eagle last week, and that may have been why Terrell Suggs made a beeline for him four plays later. The Ravens linebacker, of course, didn't have to go straight for Bradford's knee, but the play was legal, according to the NFL.

"If your responsibility on that call is to have the quarterback, then you absolutely hit the quarterback if you think he has it, but you hit him above the waist and below the neck because he's back there," Eagles defensive coordinator Bill Davis said Tuesday. "If you don't, you're going to be flagged."

Suggs was flagged for roughing the passer. The penalty should have been unnecessary roughness, but the distinction doesn't matter as much as the fact that the official reached into his pocket.

"When it's in that gray area, the NFL is going to protect the quarterbacks, period," Davis said. "They always have and they always will. That is what drives the NFL."

Still, Bradford will be more susceptible to contact because it's nearly impossible for defenders to make a distinction between what's a zone-read play and what's not in a split second. Even if Kelly doesn't call the zone-read as much as he says, it's still in his arsenal. Bradford kept twice and ran during training camp.

The threat to run is what's key to the zone-read, especially as it pertains to quarterbacks such as Bradford and Nick Foles. There's a reason Kelly keeps it, even if he doesn't have Russell Wilson or Marcus Mariota under center, and it's all about evening the scales.

"It's all in the math," Bills coach Rex Ryan said in March at the owners meetings. "It makes you defend 11 on 11, where before if all you're doing is just handing the ball with no threat of the run with the quarterback, then you got an extra defender. So it's hard to make that math work. But there's a way to make it work."

Ryan didn't give any details. There are still many who don't think zone-read-based offenses can work in the NFL because it puts the quarterback too often in harm's way. Bradford got up from Suggs' blow, but what happens when another defender is willing to risk a personal foul and tee off on a bang-bang play that may or may not be a zone-read?

"Quarterbacks get hurt in practice, quarterbacks get hurt running out of bounds, and quarterbacks get hurt when the blitz hits them and they don't recognize it," Kelly said in November 2013. "I don't look at it that way and I've never looked at it that way."

Kelly made that comment after Cardinals coach Bruce Arians had called the zone-read a "college offense." Even coaches who use the zone-read, like the Dolphins' Joe Philbin does with Ryan Tannehill, believe it should be based upon the quarterback's skill set.

Texans coach Bill O'Brien said the same thing in March. But he said even mobile quarterbacks capable of running the zone-read can't be expected to rely on those types of plays in late-game situations.

"In order to win games in this league, that quarterback at some point in time is going to have to stand in the pocket late in the game and deliver the ball accurately with guys rushing all around him," O'Brien said. "To me, the passing game is so important to winning games in a two-minute mode at the end of games."

Bill Belichick is very much like Kelly. He doesn't get caught up in trends as much as he does in the minds behind them. To him, a zone-read-based scheme will work as long as there's a coach willing to run it.

"There was a time when there wasn't much 3-4 in this league, there was a time when there was a lot of it," Belichick said in March. "There was a time when there was no run-and-shoot in this league, and there was a time when there was a lot of it.

"When the coach has control of schemes and the coaches want to run that scheme, then I think you're going to see it. Coach wants to run another scheme, then you'll see what that scheme is."

In other words, it works until it doesn't.