THOUSAND OAKS — Since 2015, when Washington head coach Jay Gruden quietly handed play-calling duties to his 29-year-old offensive coordinator, Sean McVay has earned a reputation in football circles as somewhat of a play-calling savant.

Ask those who witnessed his swift ascent through the ranks — from wunderkind assistant to youngest head coach in NFL history with the Rams to potential Coach of the Year candidate — and, inevitably, they’ll mention his memory. When it comes to football, it is borderline photographic.

“He’s like ‘Rain Man,’” says Rams offensive coordinator Matt LaFleur. “He’ll remember plays from before he was born. I’m not joking. I’ve never met somebody with the recall he has.”

Every week, McVay’s gameplan is memorized, each play filed away to be retrieved at a moment’s notice. On Sundays, his double-sided, 11-by-17 play sheet is essentially window dressing, used mostly between drives as a security blanket. Challenge him to recount any of the 306 plays he has called this season, and he is confident he could describe any of them in full detail.

To his assistants, McVay is a bionic playbook, capable of recounting random play sequences from months or years earlier.

“He’s special,” says offensive line coach Aaron Kromer. “He remembers everything.” And that’s not limited to his own team and its opponents. As LaFleur put together a play this preseason, McVay casually referenced a related sequence from a 2015 game between the Broncos and Steelers.

“I’m like, ‘How do you remember that?’” LaFleur says. “He’s just got one of those crazy minds. Everything sticks with him.”

This mastery of the playbook is no doubt a keystone of McVay’s success, like it has been for the dozen or so other NFL coaches who call their team’s offensive plays. But play-calling is more art form than science. A memorized gameplan is useless if the plan itself is thwarted.

“I think it’s the hardest job in all of sports, to be honest with you,” says Chargers head coach Anthony Lynn, hired a day after McVay and quickly handed over play calling duties to his offensive coordinator, Ken Whisenhunt.

Playcallers are often judged by their spur-of-the-moment improvisation — and blamed when those decisions go sideways — but it’s the methodology behind Sunday’s high stakes chess match, prepared through long days of work beforehand, that separates the NFL’s true playbook artists.

McVay relishes this responsibility to a near-obsessive degree. Kyle Shanahan, now the 49ers head coach, worked with McVay in Washington when he started as a quality control assistant. Shanahan noticed even then, as McVay broke down film and filed scouting reports, how much pride he put into the process.

“Sean would grind,” Shanahan says. “He takes it very personally if he makes a mistake.”

And indeed, no one has been harder on McVay’s playcalling than McVay himself. After nearly every game this season, even victories, he’s offered unprompted self-critiques, heaping any spare blame on his own shoulders.

But through five weeks of his first season in Los Angeles, Todd Gurley is thriving, Jared Goff is improving, and a once-disastrous offensive line is clicking. Overnight, the Rams have transformed from the NFL’s most moribund offense to one of its most explosive.

Behind it all is a 31-year-old play-calling maestro with a photographic memory and a preternatural grasp on the game, far beyond his age.

FLIPPING THE SCRIPT

In football’s earliest days, the quarterback typically served as his team’s de facto play caller. That first changed in the 1950’s, when legendary Cleveland coach Paul Brown sought more control, opting to use his own players to relay plays to the huddle.

It wasn’t until Hall of Fame coach Bill Walsh and his 49ers offenses of the 1980s that the NFL was introduced to the modern concept of scripting plays ahead of time. Then, Walsh’s script often included just 15 to 25 plays.

“Scripting is planning; it’s contingency planning,” Walsh told the New York Times in 1996. “The fewer decisions to be made during the game, the better. You don’t want to live by your instincts.”

The same concept stands today, although modern play cards have become exponentially more detailed … with exponentially smaller fonts.

“Depending on how long the call is, (McVay’s) can be pretty tough to read,” LaFleur says.

Most Sundays, the Rams’ playsheet will contain more than 100 plays. Each option is organized to match the order in which the Rams practice every week.

In the upper left-hand column are the offense’s 20 or so “openers,” which are exclusive to first- and second-down calls and practiced earliest in the week. Below that are priority second-and-long, “get-back-on-track” calls. Slide over, and you’ll find the third-down plays worked on during Thursday’s practice, followed by those meant for the redzone and two-minute drill, which are practiced on Friday. Those sections are then broken down into further sub-sections and contingency options.

“The whole game is right there,” McVay says.

The process of devising that plan is collaborative, carried out in a series of meetings throughout the week in which open communication is encouraged. Each coach has their own responsibility in regards to game planning. LaFleur teams with McVay on pass plays. Kromer works the run game. Quarterbacks coach Greg Olson handles third downs, and tight ends coach Shane Waldron focuses on red zone. “They’re all instrumental,” McVay says.

But McVay oversees it all, watching hours upon hours of film and jotting down possible plays in his usual notebook. Assistants describe him as meticulously organized, and, in that way, they’ve noticed the Rams’ weekly process mirroring his tendencies.

“Everyone is a creature of habit,” Waldron says. “When you have a clear idea of what you want to be and how you want to communicate, it makes the weekly rhythm that much easier.”

At his behest, McVay’s staff often begins its preparation by looking inward. Over the course of a week, the Rams focus as much time studying their own film, as they do their opponent.

This self-analysis is a crucial tenet of McVay’s coaching philosophy. He is constantly poring over past playcalls, analyzing — and doubting — his own tendencies on film, and subtly manipulating future plans. All with the intention of being a step ahead of his opponent.

“They’re watching the tape, too,” he says. “So we’re making sure we’re aware of what the defense is preparing for when they’re watching us.”

From there, McVay takes his cues from Walsh’s teachings.

“You try to play the game before the game, envision some of the scenarios and situations that can come up,” he explains. Sometimes, McVay will visualize a game from start to finish, two or three times. Until it feels “like second nature,” he says.

When he first started calling plays in Washington, McVay admits he was caught on his heels too often. He tries not to ruminate on any of his failures. But it’s the mistakes he can’t explain to his players, the ones that suggest a lack of preparation, that eat at him most.

In his short time as a playcaller, McVay has done his best to internalize those miscues and learn from them. And as the Rams head into Week 6 ranked second in the NFL in points per game and fifth in total yards, it’s the rest of the NFL that seems to be caught off balance.

KEEPING THEM GUESSING

Two weeks ago, at the end of the third quarter in Dallas, the Rams lined up in shotgun on first-and-10, with two receivers stacked to the left and one split out right. Trailing the Cowboys by five points, they were in desperate need of a spark.

So McVay sent Tavon Austin motion, knowing the Cowboys would then account for the jet sweep. As the ball was snapped, Goff faked to Austin and Cowboys inside linebacker Damien Wilson bit on the fake, just as Gurley sprinted out of the backfield and up the seam behind him.

McVay’s tweak to the original play — sending Gurley into the seam — was just subtle enough to fool the Cowboys, whom he figured knew of his jet sweep and the several variations he’s installed. Down the field, Goff hit an open Gurley, who cut on a dime to avoid the only defender in his way, before darting into the endzone for a 53-yard score. It was the kind of brilliant adjustment for which McVay has come to be known in his short time as a playcaller.

“He just has a great ability to change it up,” Washington’s Gruden says. “You don’t know what’s coming. You think, first-and-10, stop Todd Gurley. Then, they do a play-pass and launch it over your head, or they do a boot leg and hit somebody in the flat for a gain of nine. He’s just got a great way of keeping you off balance.”

McVay’s offense is built on such subtle deception, culled from those long sessions of self-analysis. The jet sweep is perhaps the best example. McVay has faked the jet sweep to Austin 19 times this season, out of several different alignments, while Austin has only actually taken the handoff eight times. Still, defenses are forced to account for him every time he sets in motion.

Pre-snap motion is a foundational part of McVay’s strategy for keeping opponents off balance. A receiver or running back has set in motion before the snap on 45 percent of the Rams’ plays this season. That’s 135 times the opposing defense was forced to make a split-second adjustment, just before the play.

It’s not his only pre-snap curveball. Recently, McVay has used quick snap counts and no-huddle more frequently. Over the past two games, the Rams have run 30 plays of no-huddle offense, compared to just 12 plays from the first three weeks combined.

A few days after the Rams narrowly beat the Cowboys, McVay is asked about how that Gurley touchdown came together. As he describes it in full detail, he grins.

“That was fun,” McVay says.

But he has to cop to something. He stole that play from the Patriots, who used it in Week 2. And he’s pretty sure they stole it from the Chiefs, who used it to burn New England for a 78-yard Kareem Hunt touchdown the week before. Neither team is on the Rams’ schedule this season. Of course, McVay had already studied them, anyway.

“It was a great play,” McVay says. “It fits with what we do because of Tavon’s ability, the same way Kansas City uses Tyreek Hill. Then, New England made it work because it stresses some of the coverage that New Orleans plays.

“We had an idea how it would play out.”

Still, McVay had prepared a contingency plan, if it hadn’t. You know, just in case.