A good deal of attention has been paid to Nick Foles' vertical passing success in Sunday's 38-7 victory over the Vikings in the NFC championship game.
Foles, who had completed just two of 13 throws of 20 yards or more before Sunday, was an impressive 4-for-5 for 172 yards on deep balls against the Vikings, including a 53-yard touchdown pass to Alshon Jeffery and a 41-yard scoring toss to Torrey Smith on a flea-flicker.
But those deep balls were set up by RPOs – run-pass option plays – that the Eagles have been using all season, and have had success with in their first two playoff wins.
RPOs are plays in which the quarterback, lining up in the shotgun, has the option of handing the ball off to the running back, throwing a pass or keeping it and running himself.
The keeping-it part really isn't a serious consideration with Foles. But that has not made the Eagles' RPO game any less effective.
"I don't think the fact that Nick isn't a threat to run is a negative,'' NFL Network analyst Brian Baldinger said.
Get insights on the Eagles delivered straight to your inbox with Early Birds, beat writer Zach Berman's newsletter for Eagles fans. Click here to sign up.
The Eagles ran 10 RPOs on 40 plays on their first six possessions against the Vikings. Foles threw the ball on six of the 10, completing all six for 52 yards. They ran the ball the other four times, gaining 27 yards.
"They've been huge for us,'' tight end Zach Ertz said of the RPOs. "Our coaches have done an amazing job of putting them into the playbook each and every week.
"It allows our offense to play fast and limits the defense from playing fast. Any time you're able to do that as an offense, you're going to be successful.''
There is nothing fancy about the RPOs. Most of Foles' throws on them have been quick slants. But the play-action with the running back freezes the linebackers and safeties just enough to free the receiver to get inside position on inside routes.
"It's just another form of a play-action pass with a more authentic play fake,'' Baldinger said. "I was anxious to see what Minnesota would do to stop it, and they were pretty much stuck in quicksand.
"It's just difficult to know how to react. It's freezing these guys. It froze [Vikings safety] Harrison Smith the other day. I saw it freeze [Cowboys linebacker] Sean Lee. Those are good football players who really weren't sure [what to do].''
RPOs have been around the college game for decades, but really weren't used much in the NFL until the Eagles hired Chip Kelly. Andy Reid, never reluctant to steal a good idea, started using them in Kansas City shortly after that, and Doug Pederson, who was Reid's offensive coordinator, has made them a part of his offense with the Eagles.
"Nick obviously is extremely comfortable with those being called,'' Ertz said. "I think it's going to be a staple of our offense going forward. It's been a staple all year. It's allowed me, Alshon [Jeffery], Torrey [Smith] and Nelson [Agholor] in the slot to get open on those things. We definitely use them to our advantage.''
When Kelly brought the RPO game from Oregon to the Eagles in 2013, a lot of people, including myself, mistakenly thought Foles' limited mobility would make him a bad fit for the offense. He was such a bad fit that he recorded the third highest passer rating in NFL history that season after replacing Michael Vick.
"When everybody thinks RPO, they think young, athletic college quarterback, and that's not what the RPO game is all centered around,'' said Eagles offensive coordinator Frank Reich. "It's centered around accurate throwing, good decision-making, and good execution. When we use it, Nick has shown a great aptitude of doing that very well.''
Indeed. Foles has executed the RPOs very well. He's made quick and usually correct reads and has delivered the ball quickly and accurately to his receivers on the slants.
"We have a method to our madness as far as why we do what we do,'' Foles said. "It all starts with execution on all fronts. On those [RPO] plays, it all comes down to execution up front [by the line] and me making a good decision.''
Baldinger thinks the fact that the offensive linemen don't know ahead of time whether it's going to be a run or pass is a benefit.
"A lot of times, what the linebackers read are the hats [helmets] of the offensive linemen,'' said Baldinger, who spent 11 years as an NFL offensive lineman for three teams, including the Eagles. "If they see the hats come up – what you call high hats – if you see that, they're not going to bite as hard. Kind of like on draw plays when they used to run draw plays.
"That's what we used to do in Dallas: stand up and get the linebackers to react to pass and have them drop back [and then run the draw]. In some ways, the fact that they can't get a read on what the offensive line is doing, that's the whole key [to RPOs].''
Patriots coach Bill Belichick and his defensive coordinator, Matt Patricia, have no doubt spent a good portion of this week scrutinizing the Eagles' RPO game and trying to figure out how to combat it better than the Vikings did.
"I think Nick has a pretty good presnap read of where to go by [defensive] alignment,'' Baldinger said. "Most of the [RPO] completions are just slant routes to Ertz or Alshon. Quick slants.