MIAMI — In March of 2018, the 49ers signed former Minnesota running back Jerick McKinnon to a four-year, $30 million contract with $18 million guaranteed. The idea was that McKinnon, who gained 2,902 yards from scrimmage and scored 17 touchdowns in his four years with the Vikings, would be the kind of satellite back who could thrive in a Kyle Shanahan offense that is based so much on defensive displacement with pre-snap motion, aligning running backs all over the field and having them do different things.

In theory, it would work. In practice, unfortunately, it hasn’t. Due to a number of knee issues, McKinnon hasn’t played a single snap for the 49ers in two seasons — on Opening Night of Super Bowl week, he was sadly reduced to interviewing his teammates as a non-factor on the field. He was placed on injured reserve before the season began in both of his seasons with his new team.

This kind of injury to a potential force multiplier would wreck the schematic intentions of a lot of teams. Not Shanahan, and not his 49ers. Shanahan is the most creative and adaptive offensive play-designer in the NFL today, his run designs are as close to art as you’ll find in pro football, and as a result, when he’s missing a crucial piece, he’s able to replace it in the aggregate.

Fast-forward to the 2019 NFC Championship game when running back Raheeem Mostert, who had been cut by six different teams before the 49ers took a chance on him, ran 29 times for 220 yards and four touchdowns against the Packers in the 37-20 win that propelled San Francisco to its first Super Bowl since 1994. Kyle’s father Mike Shanahan was the offensive coordinator for that ’94 49ers team, and the elder Shanahan passed along a number of ideas, especially in the zone run game, that would help his son design his own run schemes that would make running backs incredibly effective in a general sense, and relatively fungible in an individual sense.

Though the NFL has obviously become a passing league, there’s still a pronounced schism between new-school analysts who believe that you should never place too much value on an individual running back, and old-school smash-mouth truthers who still want to “run to win.” While there isn’t a monopoly of truth on either side, the real answer seems to lie in the effectiveness — or not — of the run games that are designed for those backs. Mostert was an NFL afterthought until he landed in Kyle Shanahan’s scheme, and then, he was an overnight sensation. Backs like Terrell Davis, Mike Anderson, and Reuben Droughns were similarly elevated by Mike Shanahan’s run schemes with the Denver Broncos of the 1990s and early 2000s.

This successful philosophy allowed Denver to, for example, trade Clinton Portis to the Washington Redskins for Champ Bailey in 2004 without breaking a sweat. Mike Shanahan understood that, regardless of the system, it was going to be more difficult to find a Hall of Fame cornerback than it would be to take a sixth-round pick like Terrell Davis and transform him into a Hall of Famer based on the benefits of intelligent design. Denver was on the vanguard of the new mindset; Washington valued running backs in more of a vintage fashion. Denver also got a second-round pick in that trade; they used it to select running back Tatum Bell out of Oklahoma State, and Bell became another back who benefited for a time from Mike Shanahan’s acumen. To prove the point further, Bell took Portis’ jersey number 26.

Not that we should start fitting Mostert for a gold jacket just yet, but the effectiveness of the 49ers’ run game has set the league on edge, and goes against most modern trends. They come into Super Bowl LIV ranked seventh in Football Outsiders’ opponent-adjusted offensive efficiency metrics. They are one of two NFL teams in 2019 — the Ravens are the other — to run the ball more than they’ve passed it. This trend has a serious upswing in the postseason, when Shanahan turned his run game loose on the Vikings and Packers, turned quarterback Jimmy Garoppolo into a 1972 Bob Griese handoff machine, and both out-fought and out-thought those defense with a run system that not only took advanced zone concepts from Shanahan’s dad, but also employed pre-snap motion at an 80% rate, implemented all kinds of power-blocking stuff from trap plays to wham concepts, and presented itself as impossible to stop although both Minnesota and Green Bay knew exactly what was coming.

Michael Robinson, who was drafted by the 49ers in 2006 and later found success and a Super Bowl ring with the Legion of Boom-era Seahawks, told me this week that the ability to run the ball right down everybody’s throat is actually far more about exquisite planning than the ability to win a series of force-on-force scrums.

“It’s Kyle Shanahan, man. His ability to out-leverage a defense, whether it’s through motions and shifts, or bubble screens and halfback screens, reverses… or just the, I don’t want to say ‘ignorance,’ but the ignorance about running the football. You can have nine [defenders] at the line of scrimmage, and Kyle will say, ‘OK — but we’re going to attack here, and we’re still going to run it, and you still have to stop it. It’s a defensive mentality on the offensive side of the ball, and not a lot of offensive play-callers have that. When you talk about it in terms of what makes this run game unique and special, it’s the play-callers.”

Robinson, who now works as an NFL Network analyst, revealed that Shanahan values his run designs so much, he can’t help but show the film to the whole family like an over-eager dad at the end of a long vacation.

“I’ve talked to guys in that locker room, and every time they have a schemed play — a run call he thinks is going to be really good — he coaches it in front of the whole team. Even the defensive players. And he’ll say, ‘Guys, if this doesn’t work at the stress point of the play, like the tackle blocking down is the stress point, often it’s going to be because this guy [the blocker] didn’t do his job. It adds a level of accountability. Everybody on the team knows what they’re looking at. Defenders know, ‘Oh, the run game is going to eat this week because I saw it in the team meeting room.’ They know all the coaching points. You can always have a great team when your team has a great football I.Q., and I think Kyle and all those coaches in San Francisco are building that.”

Shanahan has also built belief in his run game to the point that plays that would scare the daylights out of other coaches just seem to work for the 49ers. Against Green Bay, with 6:31 left in the first quarter of the championship game and the score knotted at 0-0, Shanahan called a Mostert run on a trap play on third-and-8. Not exactly the most common call, but the result was almost predictable — assignments executed correctly against a defense with their ears pinned for the pass, and a 38-yard touchdown.

Mike Person, the right guard who pulled inside left tackle Joe Staley on this play, told me this week that Shanahan’s blocking concepts are so varied, it has taken a while for everyone to get on the same page all the time. But once that happened, the 49ers’ front five was able to see the game at a higher level, with more prominent and interesting results.

For the Chiefs, who come into this game ranked 29th in Football Outsiders’ run defense metrics, and similarly vulnerable against backs who hit the second and third levels quickly (as is native in Shanahan’s offense), the challenge is obvious. Kansas City’s defenders might be rightfully outraged at the lack of respect their pass defense has received throughout this process, but the run defense? That’s a different story. And when you talk to them about San Francisco’s run game, players and coaches don’t talk about stopping Mostert or Matt Breida or Tevin Coleman or anybody else who suits up as a running back on that roster.

The fixation is entirely on stopping Kyle Shanahan. As much as any coach at any level of football right now, Shanahan is his team’s most valuable offensive player.

“Hopefully, it doesn’t affect what you do,” Chiefs defensive line coach Brendan Daly told me this week. “We’re playing with great technique and fundamentals and faith in our progressions and keys, to where whatever they do, we should be able to defend it. That’s the goal, obviously. Now, they do present a number of challenges. They do a great job with their schemes. They do a fantastic job with zone-scheme blocking. They do a great job with gap-scheme blocking, and things of that nature. They throw a lot of different motions and formations and window dressing at you. At the end of the day, the thing we’re going to have to a good job of is trusting our process and playing good, physical, sound football at the line of scrimmage. You can’t get enamored with this, that, and the other thing — we’ve just got to go out and play.”

San Francisco also has two blockers in fullback Kyle Juszczyk and tight end George Kittle who will align all along the formation, whether in static place or with pre-snap motion, to make things even more dizzying.

“They use motion with their personnel to get into some different formations, and they force the defense to adjust,” Daly said. “We’re going to have to do a great job in terms of communication in response to their pre-snap shifts and motions, and making sure when the ball’s snapped, we’re lined up properly and we’ve got our gap responsibilities handled. They present a number of challenges in that regard, and they do it with extremely skilled personnel.”

Robinson excitedly agreed. It was easy to tell that he would have loved to play in this offense. Most running backs would. For most fullbacks, you can double that.

“Oh, it’s everything,” Robinson said of Shanahan’s motion concepts. “Because at the end of the day, they want to make sure [the defense] did their homework. So, if I’m motioning a guy across, and there’s a defender running with him, they’re in man coverage. If a guy motions across and nobody moves… either a blitz is coming, or maybe they haven’t seen this motion. Maybe [the quarterback] ought to toss the ball to the motion guy going across the formation. You get these little things from a defense, and I think Kyle Shanahan does the best job of using those tells against the defense.”

That adds the element of rookie receiver Deebo Samuel, who has replaced McKinnon to a point as Shanahan’s satellite flyer on reverses and end-arounds. While Samuel has proven adept in the passing game, he’s also run the ball 17 times for 208 yards and three touchdowns.

This 30-yard touchdown run against the Seahawks in Week 17 featured a misdirection pitch, and Juszczyk hammering the downfield lane by blocking cornerback Shaquill Griffin and linebacker K.J. Wright out of the play at the same time.

Kansas City’s defense should expect more of the same. Or, to be more specific, the Chiefs should prepare for everything, and expect things they haven’t seen on tape no matter how much they’ve studied it. That’s what Kyle Shanahan has created — a system that is injury-proof, player-transcendent, and entirely Super Bowl-worthy.

Touchdown Wire editor Doug Farrar previously covered football for Yahoo! Sports, Sports Illustrated, Bleacher Report, the Washington Post, and Football Outsiders. His first book, “The Genius of Desperation,” a schematic history of professional football, was published by Triumph Books in 2018 and won the Professional Football Researchers Association’s Nelson Ross Award for “Outstanding recent achievement in pro football research and historiography.”