On Sunday, if you listen to the Super Bowl LIV television broadcast, you almost certainly will hear the announcers say the key to the San Francisco 49ers’ offense is “outside zone.”

The play concept, while not new, has been instrumental to San Francisco’s success. The 49ers, 4-12 last season, sit a win over the Kansas City Chiefs from their first Super Bowl championship since the 1994 season, in large part because of a rushing attack that ranked second in the league this season at 144.1 yards per game and became an integral part of the team’s identity.

The NFL remains a passing league, but the 49ers used a run-heavy offense to blow past the Minnesota Vikings and Green Bay Packers in the playoffs by taking advantage of the play-calling of Coach Kyle Shanahan and a trio of speedy running backs — Raheem Mostert, Matt Breida and Tevin Coleman. Quarterback Jimmy ­Garoppolo attempted only eight passes in the 37-20 win over the Packers that gave the 49ers the NFC title.

How does outside zone work? Where did it come from? And what does it mean for Sunday’s matchup? Let’s take a look:

How does outside zone work?

Outside zone is a running play on which offensive linemen focus their blocks on zones, or spaces on the field, as opposed to specific defenders (which is referred to as man-to-man blocking). It calls upon linemen to caravan toward the sideline and push back whichever defenders are in the way. Running backs are asked to look for three options: “bounce” outside, “bang” a cut upfield between the linemen or “bend” on a cutback across the formation.

“You need [running backs] who find the lane, put their foot on the gas pedal and get 0 to 10 fast,” ESPN analyst Matt Bowen said.

The scheme can be boom-or-bust. No run play gets stuffed for no gain or a loss of yardage more often, and no run play yields more plays of 20-plus yards. In pursuit of the type of chunk plays that are necessary to win in the modern NFL (more commonly achieved through the passing game), teams have to keep hammering away in search of pay dirt. This is true even for the 49ers, who ran it better than any other team on their way to the Super Bowl.

“Outside zone is a war of attrition,” said Dave McGinnis, a longtime NFL coach. “The people who are successful with it are patient.”

What’s the origin of outside zone?

The importance of zone blocking traces to Kyle Shanahan’s father, Mike, who helped innovate the idea in the early 1990s to counter the Pittsburgh Steelers’ zone blitz. Steelers defensive coordinator Dom Capers disrupted the offensive line’s man-to-man blocking assignments with concepts such as blitzing a linebacker and dropping a defensive end into ­coverage.

Mike Shanahan, then head coach of the Denver Broncos, and assistant Alex Gibbs realized something: Offensive linemen should block an area rather than a man.

The scheme was simple, yet each play is delicate. If any defender penetrates the blocking wall, the run can be stuffed. This puts extreme pressure on both teams to control the line of scrimmage, and it emphasizes why everyone must be patient — coaches in their play-calling and players in their execution.

“Timing is everything,” said Packers guard Billy Turner, who plays in the same scheme.

Maintaining every block on every play is hard, so the hit rate is low. But even if an offense only totals 20 yards on its first seven or eight rushes, the coach’s philosophy is this: My players will do their jobs more often than your players will.

“Boom, then there’s a 60- or 70-yarder, and the defender’s saying, ‘He only had one long run!’ ” said Dennis Thurman, a longtime defensive coach. “But how disciplined were you? [Outside zone] only takes one guy breaking down.”

That flexibility proved difficult for opponents to defend. The Broncos won Super Bowl titles in the 1997 and 1998 seasons, and Terrell Davis, the quintessential “one-cut” running back who thrived in Shanahan’s outside zone scheme, landed in the Pro Football Hall of Fame.

How do the 49ers use outside zone?

Kyle Shanahan hasn’t changed the core of the approach that his father created.

“It looks the same to me,” Thurman said. “It’s a simple concept, but it’s hard to stop.”

One similarity that Shanahan uses in his favor is a personnel grouping — two-running-back sets — that is less common in today’s game. Defenses aren’t used to facing offenses with such a power run-heavy approach — even other outside zone-heavy teams, such as the Los Angeles Rams, typically operate out of one-back, three-wide-receiver lineups — but the 49ers have a fullback in Kyle Juszcyzk and a tight end in George Kittle who are powerful blockers and still versatile enough to factor into the passing game.

The biggest difference in ­Shanahan’s version of the outside zone is the way he dresses up plays to confuse the defense. He runs multiple plays out of multiple formations to avoid developing tendencies that opponents can identify in advance. He deploys presnap motion and play-action at rates that rank among the highest in the NFL, creating what defenders refer to as “eye candy” — and forcing the defensive players to think longer and play slower.

“Speed is everything,” McGinnis said. “If you make a slow, correct decision on defense, you’re wrong.”

What does it mean for the 49ers vs. the Chiefs?

The Chiefs enter Sunday’s game understanding that the key to stopping the 49ers’ offense is slowing the outside zone. Their best weapon in this effort might be defensive tackle Chris Jones, who is a disruptive interior force but is dealing with a calf injury. Bowen identified him as the Chiefs’ most important player.

“If this is a line-of-scrimmage game, San Francisco is Super Bowl champion,” Bowen said. “If they can control the offensive front, it’s over.”

Simply slowing San Francisco’s rushing attack won’t be enough to guarantee a Chiefs victory. The threat of outside zone unlocks the rest of the 49ers’ offense. They are one of the most balanced teams in the league, running the ball almost 52 percent of the time, and they have found success using play-action, particularly on first down. They pull linebackers closer to the line of scrimmage and clear throwing lanes for Garoppolo.

“It’s brilliant,” Bowen said. “They’re consistently putting defensive players in conflict and testing their eyes.”

The defense’s uncertainty helps the 49ers’ offensive line give ­Garoppolo time, and his 8.7 yards per attempt and 115.5 passer rating from a clean pocket both rank fifth in the NFL. Even though outside zone keys the offense, the 49ers’ options make them dangerous.