A longstanding NFL trope says it's hard to beat a team three times in one season.

You're bound to hear it regurgitated as the Los Angeles Rams and San Francisco 49ers prepare to play in the NFC championship game. Don't believe it.

2 losses to the 49ers don't give the Rams an edge

The familiar matchup between NFC West foes will mark the third time the rivals meet this season. The Rams, despite being the higher seed and the betting favorite at -3.5 with BetMGM, have been on the losing end of both previous matchups. The 49ers rolled to a 31-10 Week 10 win at home before eking out a 27-24 overtime win at SoFi Stadium in Week 18 that they needed to make the postseason.

Now, here they are fresh off two straight playoff wins with a chance to vanquish their division foes a third time for the right to play in the Super Bowl. And some folks will knock their chances simply because they've been the better team twice already this season.

While there are certainly plenty of rational reasons to pick the Rams over the 49ers, this is not one of them. It's not based in reason. It's not supported by history.

This NFL myth doesn't stand up to reason

The logic — or lack thereof — recalls the gambling fallacy casinos exploit to lure players to roulette wheels. If red's been hot, black's bound to hit next. It's due, right?

Roulette tables proudly display past results on glowing screens as if they have anything to do with future spins. Some bettors will put their chips in play simply because they've spotted a trend they believe is bound to turn around.

Each spin, of course, is independent of every spin before it. Assuming an honest wheel, red has the same chance to hit as black every time even if red's hit for 10 straight spins. Meanwhile, green ensures that the house has the edge regardless of what bet you place. So long as you're putting chips on the table, the house is happy.

It doesn't work in roulette, and it doesn't work in football

This appears to be the rationalization behind the NFL's playoff myth. Surely the 49ers are at a disadvantage on Sunday simply because it seems hard to win three in a row — even though they've already done 2/3 of the work to get there.

The logic is flawed even while the roulette comparison isn't perfect. Unlike spins of the wheel, past results between opponents on football fields most certainly influence future results. Players and coaches learn from previous matchups and take that knowledge into subsequent games. And opposing teams aren't equitable adversaries like red and black on a roulette wheel.

But this is a difference that reason dictates actually supports the previous winners. A team that's won two out of two games has already demonstrated an edge in the matchup, even if via a small sample size.

History supports the 2-time winners

If logic doesn't sway you, then take a look at the history books. Statistics tallied by the Elias Sports Bureau and published by ESPN in 2018 showed that 20 such matchups had taken place in the NFL playoffs since the 1970 AFL/NFL merger. Of those matchups, the teams that swept the regular season went on to win the playoff matchup 13 times.

The NFL has seen two such matchups since. The 2017 New Orleans Saints swept the Carolina Panthers then went on to beat them a third time in a wild-card game. Last season, the New Orleans Saints swept the Tampa Bay Buccaneers before Tom Brady and company ended Drew Brees' career in the divisional round en route to a Super Bowl title.

It all adds to 14 playoff wins in 22 modern-era matchups for the teams that swept the regular season, which adds up to a 63.6% win rate. Because of course the team that's won twice already has an edge more times than not.

So what about Rams-49ers on Sunday?

Will Sunday's game favor the two-time winner that's won nearly two out of every three previous matchups? This matchup looks harder to pick than most to pick.

While the 49ers swept the Rams, the Rams (12-5) were two games better than the 49ers (10-7) in the regular season. They won the NFC West. On the other hand, Kyle Shanahan's 49ers didn't just sweep Sean McVay's Rams this season. They've won six straight in the matchup dating back to the 2019 regular season. Their seventh-ranked offense and third-ranked defense were both better than the Rams' corresponding units in terms of yards and yards allowed during the regular season.

Then again, the Rams are better on both sides of the ball than they were to start the year thanks to the midseason acquisitions of Von Miller and Odell Beckham Jr., who are both paying dividends at the right time.

These are all factors to consider if you're thinking about placing bets on either team. But whatever you do, don't take the Rams on the moneyline simply because you've heard that it's hard to beat a single opponent a third straight time. It's just not true.