SANTA CLARA -- It did not come as a surprise to those in the huddle when 49ers coach Kyle Shanahan dialed up a running play on a third-and-8 situation in the first quarter of a scoreless game.

Those 11 players on the field might have been the only ones who weren't shocked by the decision.

“Our coach is a genius,” 49ers right tackle Mike McGlinchey said.

Shanahan’s call and running back Raheem Mostert’s sprint through the Green Bay Packers defense was a key play in the 49ers’ 37-20 victory in the NFC Championship Game on Sunday at Levi’s Stadium. The victory advances the 49ers to Super Bowl LIV on Sunday, Feb. 2, against the Kansas City Chiefs.

The 49ers cruised to a 27-0 lead at halftime, and it all started with a unique play call given the circumstances.

Shanahan told his offense throughout the week that they could exploit some of the Green Bay Packers’ exotic third-down defenses with third-and-long trap plays out of the shotgun formation. Shanahan believed he could use the aggressive tendencies of Packers defensive coordinator Mike Pettine against him.

With the ball on the Green Bay 36-yard line, the 49ers could potentially have gone for it on fourth down had Mostert gotten close to the first down. Or the 49ers could have gained some yards to merely give kicker Robbie Gould a closer shot at a field goal.

“It would have depended how close it was, but if not we would have been happy with a field goal,” Shanahan said. “For him to take it to the house was a lot better than anticipated.”

On the play, Packers linebacker Kyler Fackrell lined up over the left guard and was allowed an unblocked path into the backfield. He stumbled, and right guard Mike Person came from the other side to block him, keeping him out of the play.

Outside linebacker Preston Smith got upfield on the left edge but Mostert sped past him after taking the handoff from quarterback Jimmy Garoppolo.

Left guard Laken Tomlinson blocked elite pass-rusher Za’Darius Smith and left tackle Joe Staley sealed off an inside linebacker to open a big hole for Mostert.

Mostert outraced everyone to the end zone for a 36-yard touchdown run – the first of his four touchdown runs on the day. It was even better than how Shanahan drew it up.

“He’s ballsy and he trusts us,” McGlinchey said of Shanahan. “That’s the coolest thing. He does these things in the game plan and he views everybody, all 11 guys on offense, as a weapon. He puts us in matchups where we can succeed. That was something we worked at all week and something we knew we could exploit.”

Said Jimmy Garoppolo, “It's part of the game plan, and Kyle called it at the perfect time. It was a great set up. It was awesome.”

A week ago, the 49ers ran the ball 47 times in a blowout victory over the Minnesota Vikings in the divisional round of the NFL playoffs. They were even more run-heavy on Sunday, as Garoppolo completed just six of eight passing attempts for 77 yards.

Shanahan’s play call on third down set the tone for the remainder of the half, and the remainder of the game. The Packers never were able to unleash their pass rush – in large part because the 49ers rarely dropped back to pass.

“We were going to hit a run play on a third-and-long, but it had to be the right situation,” Staley said. “They got into the (defensive) front we wanted.”

Said Person, “Nobody is expecting that on third-and-8, so he (Mostert) jets upfield and that’s taking advantage of what they want to do. You give up some penetration on that, and all he needs is a little seam.”

Once Mostert gets into the clear, he almost is impossible to catch because of his breakaway speed. On Sunday, he set the 49ers record for most rushing yards in a game – regular season or postseason. Mostert rushed for 220 yards and four touchdowns in 29 attempts.

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Shanahan said he figured they were going to run the ball a lot. But he never would have thought there would be such a large disparity. The 49ers attempted 42 run plays and called just nine passes.

“We were hoping to do something like that going in,” Shanahan said. “But you never plan for it to be like that. When you're watching how the guys were running and everything, and then watching how our defense was playing, it made it very easy to stick with, even the third downs and stuff.

"The guys played as aggressive as any team I've been on, and they made it very easy to call plays.”

Programming note: NBC Sports Bay Area feeds your hunger for 49ers Super Bowl coverage with special editions of “49ers Central” all week (5:30 p.m. Monday and Wednesday; 8:00 p.m. Tuesday and Thursday; 6:00 p.m. Friday)