New England’s Shea McClellin performs The Leap during a Ravens field goal attempt this week, a technique that is being both condemned and praised around the NFL this season. (Jim Davis/The Boston Globe)

As Justin Tucker measured his steps to line up a field goal Monday night, Shea McClellin stood on the other side of the line, a visual counterbalance to Tucker, and measured his own. Tucker had not missed a kick all season. The New England Patriots had discovered secrets Baltimore’s field goal unit had hidden in plain sight. In the NFL, even the most routine plays can unfurl an entire universe.

McClellin and the Patriots had studied film for weeks for what happened next, one of the most exciting — and controversial — plays in football: McClellin sprinted, leaped over both lines and blocked Tucker’s field goal attempt. The leap helped key New England’s victory and provided the most recent example of a rare, exhilarating play gaining popularity in the NFL.

For some, The Leap is a delight, a perfectly legal combination of exemplary teamwork and thrilling athleticism. For others, The Leap is a menace, a loophole-exploiting trick that places players’ safety at unnecessary risk.

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The play has made a distinct impact on this NFL season. In Week 10, Broncos special teamer Justin Simmons leaped over the New Orleans Saints’ line late in the fourth quarter and blocked what would have been a go-ahead extra point. Teammate Will Parks scooped the ball and ran to the end zone for a two-point conversion, flipping a one-point deficit to a one-point lead, effectively stealing a victory.

The hands of Broncos safety Justin Simmons, right, as he blocks the Saints‘ Wil Lutz’s extra point attempt last month. (Jeff Haynes/AP)

“Just time it up right,” McClellin said Monday night. “That’s all you’ve got to do: time it up right.”

But The Leap contains so much more, in both preparation and execution, beginning with the technique of the most overlooked player on most NFL rosters.

“It’s all about how the snapper in that part of the play does his job,” Redskins long snapper Nick Sundberg said.

As Sundberg explained, NFL teams teach two techniques for long snappers. The first is to snap and immediately lift your head, then lean to one side to help guards block. When Sundberg arrived with the Redskins in 2010, special teams coach Danny Smith repeated the same instructions: Chest up, head up, arms out.

“As soon as the ball comes out of my hands, my head’s coming up,” Sundberg said.

For that reason, Sundberg does not worry about an opponent leaping over him to block a field goal try. The would-be leaper would risk clipping his cleat on Sundberg and falling or bowling him over and drawing a penalty.

“I don’t keep it in the back of my mind at all,” Sundberg said. “I trust my technique will take care of it, and teams won’t try that against us, because of the way I protect post-snap.”

The other way teams teach long snapping is for the snapper to rifle the ball between his legs, then put his fists on the ground. It allows for the snapper to buttress himself and maintain leverage against rushing defenders. It’s also a relic from the years before the NFL defined snappers as defenseless players, thus making it illegal to smash them immediately after a snap.

“Back then, they could tee off and destroy us,” said Mike Leach, who retired last year after long snapping for 16 seasons, the last seven in Arizona . “So coaches used to teach, ‘Snap and get low, try to get as low as you can to brace yourself.’ There’s still some of that held over teaching that technique, even though in my opinion, there’s no need for that anymore.”

So, guess which technique Ravens long snapper Morgan Cox uses? He leans forward, with his fists on the ground, after he releases the ball. In fact, the entire Ravens line kneels low to protect on field goals.

“If you go through all 32 teams and watch who has the lowest pad level in the NFL, Baltimore is easily No. 1,” Sundberg said. “Their guards, tackles, tight ends, they’re all in a four-point stance. I was there in 2009, and they preach low, low, low — low man wins. You know how the Patriots are. They’re always scheming and game-planning.”

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Two weeks before the Patriots played Baltimore, McClellin said, special teams coach Joe Judge started to implement the play. Defensive tackles Malcolm Brown and Alan Branch charged forward low to the ground, inducing Baltimore’s interior lineman to drop their pads even lower. Because Tucker always took his steps and started his approach to the same beat, McClellin could focus on his perfectly timed sprint and leap over the line just as Cox threw the ball between his legs.

“It looked like they timed our snap and the guy made a hell of a play,” Tucker said. “I don’t know what happens in their meetings, but the guy made a good play on the ball.”

“Joe Judge did a great job of designing the play,” Patriots Coach Bill Belichick said. “We worked on it all week and just felt like we could take advantage of that. Shea really executed it perfectly, as did the guys up front.”

The play delivered everything a fan could want from football: surprise, action, choreography, athleticism. And yet, some within the league want the play banned.

No one doubts the present legality of The Leap. Rule 12, Section 3 of the NFL rulebook details what is prohibited on a kick: jumping or standing on a teammate; placing a hand on another player to gain extra height; lifting a teammate; and leaping over players at the line of scrimmage and landing on someone.

The operative clause is “and landing on someone.” And some coaches would like to see that qualifier eliminated.

The NFL’s Competition Committee has discussed the play in the past and plans to review it again this offseason, one league official said.

“It’s bad for football,” Cardinals Coach Bruce Arians said earlier this season, after Seattle’s Bobby Wagner jumped over Arizona’s line to try to block a kick. “Because what you’re going to have to do now is start having centers raise their face up and get kicked in the face. And things that are just dangerous to the players. I think it’s a dangerous play as it is and should be taken out of the game.”

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Snappers themselves don’t see it that way. Foremost, they assume risk upon signing a contract. “I don’t know if there is a safe play in football, if you look up the definition of ‘safe,’ ” Sundberg said.

Because Sundberg espouses the technique of lifting his head after snaps, he would be at risk of a would-be leaper kicking or kneeing him in the face. He’s willing to live with that result, protected in his mind by the rulebook.

“It’s a 15-yard penalty and unnecessary roughness,” Sundberg said. “All sorts of things are happening for the good of our team if that happens. That’s the risk I take on every play in the game. . . . I don’t think you can say just from a safety standpoint, ‘It’s too dangerous, get it out of the game.’ You could probably come up with 100 different plays before that one.”

Said Leach: “I don’t see any reason why it should be illegal. If a guy wants to time it up to gain an advantage, or if a guy wants to take the risk and jump over somebody, it’s up to the team who’s kicking the field goal to do something about it. Change up their rhythm or come up with a different technique.”

For now, at least, the play remains legal. It could even tilt, if not decide, a playoff game. The defender who jumps will receive the most attention. But he will know it takes so much more to make the leap.