INGLEWOOD, Calif. — The N.F.C. championship game displayed two different teams, two different fan bases and two different strategies for building a roster.

There’s how the Los Angeles Rams did it, dotting their locker room with some of the league’s biggest stars and trading away draft picks at will with the hope of playing the Super Bowl in their sparkling $5 billion stadium.

And there’s how the San Francisco 49ers did it, drafting players that fit their style of grinding other teams with slow and physical plays. Those clashing approaches provided a back-and-forth exchange in Sunday’s game, but in the end, the Rams prevailed, concluding a season in which they made serious gambles to try to reach the championship game.

Los Angeles won, 20-17, to earn a place in the Super Bowl, where they will face the Cincinnati Bengals. San Francisco quarterback Jimmy Garoppolo tried to escape an Aaron Donald blitz on third-and-13 late in the fourth quarter and flung a pass to his running back. It tipped off his hands and Rams linebacker Travin Howard grabbed it with a little over a minute remaining.

After Matthew Stafford knelt out the clock, a cannon fired at SoFi Stadium and Rams fans roared over the sea of visitors in red jerseys and T-shirts who had dominated the venue for most of the evening.

It is rare for division rivals to meet three times in one year, let alone with one of the games having a Super Bowl berth on the line. Adding to the intrigue, this season’s third edition of the matchup pitted friends and former colleagues, 49ers Coach Kyle Shanahan and his Rams peer Sean McVay, against each other once again, their deep familiarity whittling down the counters each had left.

Shanahan had bested his rival in their previous six meetings. In Week 18, with a chance to secure the No. 2 seed and prevent the 49ers from entering the postseason, the Rams squandered a 14-point halftime lead at home and lost in overtime.

The 49ers capitalized on their new life in the postseason by going on the road to dispatch the inconsistent Cowboys and then the top-seeded Packers, in blizzard-like conditions, to set up Sunday’s grudge match.

In the first half, the Rams looked uncharacteristically sloppy early. Stafford threw an interception on Los Angeles’s second drive as he tried to force a touchdown pass through double coverage to Cooper Kupp. Outside the 16-yard touchdown strike to Kupp to open the second quarter, the first score of the game, Stafford and his receivers looked out of sync, with Kupp and Ben Skowronek dropping passes that could have turned into scores.

After Deebo Samuel followed the Rams’ touchdown with a 44-yard touchdown off a screen pass from Garoppolo, Los Angeles’s Pro Bowl kicker, Matt Gay, who missed only two field goal attempts in the regular season, fell well short of the uprights on a 54-yard attempt.

San Francisco led 10-7 at halftime, content to follow its script of short plays and a heavy dose of Samuel, and then elongated its lead in the third quarter when Garoppolo threw a 16-yard touchdown to George Kittle on a busted coverage.

Los Angeles, though, kept searching for ways to break through. Stafford discharged another touchdown pass on a corner route to Kupp that resulted in a 11-yard catch. On defense, the Rams forced the 49ers to punt, though McVay challenged the official ruling of Kyle Juszczyk being down by contact on his third-down run. The call was upheld leaving Los Angeles without any timeouts down the stretch.

On the next possession, Gay punctuated a 40-yard drive with a field goal that tied the game at 17 with 6 minutes 49 seconds remaining.

It was the Rams’ turn to force the 49ers into sloppy play, with Garoppolo hurried into three incompletions and a delay-of-game penalty and the 49ers being forced to punt after a 23-second drive.

With the ball back in his hands, Stafford found four different receivers before connecting with Kupp again for a 25-yard gain to the San Francisco 12-yard line. Unable to breach the goal line, the Rams kicked a 30-yard field goal to go ahead, 20-17, with 1:46 remaining, leading to the game’s final sequence.

Donald, the defensive tackle at the center of the team’s pass rush, had been to that point exhorting his teammates from the sidelines and had called the team’s defense to an impromptu huddle. With the game on the line, they held, forcing Garoppolo into two incompletions before Donald, the Rams’ first-round draft pick in 2014, fittingly harangued Garoppolo into his final costly mistake of the season.