The Eagles' Super Bowl victory brought into focus their offense's extensive use of RPOs — plays that are conceived as runs, but depending on how the defense reacts, can become passes.

Many other offenses already used such concepts, but the Eagles' success doing it behind two quarterbacks, Carson Wentz and Nick Foles, seems to have made RPOs the hot offensive topic of 2018.

Opposing defenses have spent a lot of time during the offseason scheming how to slow an Eagles attack that generated 79 points and  994 yards in the NFC Championship Game and the Super Bowl, after averaging a healthy 28.6 points per game in the regular season.

>>READ MORE: The Eagles' RPOs have NFL defenses searching for an antidote

One defensive group is acutely aware of how hard it is to defend against RPOs, after facing them every day in practice. That would be the Eagles' defense, headed by coordinator Jim Schwartz.

"RPOs aren't new. Been around for a while," Schwartz said recently. "The increased use of them is probably a little bit more new, but it's a challenge that we've dealt with for long time now.

"You can't overplay anything. I think that's probably the biggest thing. If you're overplaying the run, you make yourself susceptible to the pass; if you're overplaying the pass, you make yourself susceptible to the run. I think that's been the basis of that [success]."

>>READ MORE: NFL kickoffs are changing, and players aren't happy

With the Eagles' offense, if the defense steps up to stop the run, the quarterback often throws a slant, sometimes against the flow of the would-be run. This at the very least affects a defense's aggressiveness, its ability to rally to the ball.

Strongside linebacker Nigel Bradham said the reason offenses are going more to RPOs is simple.

"Because it works," Bradham said. "It's a run play, but you've got the option to pass, as well. Linebackers, you get that window, that seam, behind them, because [the linebacker has to] bite down to stop the run.

"You just gotta have a good key on the quarterback. I think it really takes a lot of studying. A lot of studying and just being able to pick up what type of [quarterback] it is … Like, Eli [Manning] is a real good guy at doing it."

Kamu Grugier-Hill is trying to win the starting weakside linebacker spot vacated by the release of Mychal Kendricks.

"If a linebacker bites the run, they throw the slant, or if the linebacker stays back, they run the ball," Grugier-Hill said.

Grugier-Hill said he thinks RPOs only really work against zone pass coverages, though other Eagles defenders said they wouldn't go that far. But since RPO routes tend to involve levels – a receiver will be running a pattern in front of another receiver – you might be better situated to defend if you're in man coverage. Unless, of course, the offense uses rub, or pick, routes, as the Eagles often do.

Grugier-Hill said one way to take away the mystery is to make the run option tougher without bringing more players into the box.

"You can cancel the gaps inside [have the defensive linemen slant, rather than play straight-up], so a linebacker doesn't have to come down; you can do a lot of things," Grugier-Hill said.

An offensive group that run-blocks as well as the Eagles do can make such a call even in what seems to be an obvious passing situation, and go ahead and execute the run, even if the first down marker is several yards away.

"Teams do it in unpredictable downs; we do it in unpredictable downs," cornerback Jalen Mills said. "You see teams do it on first-and-10; they may do it on second-and-9. It's very, very unpredictable … That's what you want. As offensive guys, you want to keep defensive guys on their toes. I hate when I don't know what's about to happen."

So does defensive end Chris Long, who often is lined up in a Wide 9 setup, ready to zoom in on the quarterback as he drops back to pass.

"It might make you a little less aggressive, as a d-lineman," Long said.

Still, Long has his orders.

"I'm going to rush like it's a pass until I get my key that the ball's been released and I gotta plant my foot in the ground and go run," Long said.

The "go run" part is trickier with RPO passing, Long said.

"I think it can also make you a little bit fatigued if they're throwing the ball sideline-to-sideline. That's different from a vertical pass play, where [a defensive lineman would] kinda run five yards because you know you're not in the play. An RPO, the ball might be sideline-to-sideline; you've got to run right back, you gotta run 40 yards back and get in the huddle."

Long said this was not how it was when he entered the NFL in 2008 with the Rams, back when men were men and runs were runs and passes were passes, goshdarnit.

"The way I look at football now, everything's a damn RPO. Everything's spread out," Long said. "When I got into the league, it was a lot more power, counter, it was pro-style play-action passes, shots [downfield]. Now, especially if you're on a good d-line, I feel like everything speeds up. They do that intentionally. And if a team features RPOs or screens or things to slow a d-line down, they're going to do it.

"When I got in the league, people would pound the football, then take your deep shot off that. I think of RPO as more of a quick game."

Safety Malcolm Jenkins said the RPO tendency toward trying to stretch defenses horizontally creates opportunity for defenders. If you do your job, don't get gashed with a 30-yard run or don't miss a tackle that turns a 10-yard gain on a slant into 40 yards, the offense really has to work to score. The more snaps a drive takes, the greater the possibility of a killer penalty, sack or turnover.

"At the end of the day, you want them to throw RPOs," Jenkins said. "We have a lot of faith in our corners tackling in the open field. If they throw it out there, there's two things that are going to stop an RPO – that's great tackling on the perimeter, but also effort from the interior. Corners, tackle, safeties, linebackers, and d-line turn and run. Even if that corner misses, as long as he misses to the outside and turns it to the inside, it's a limited game. We can play that game all day."