Why aren’t the 49ers prime-time players Sunday?

The 49ers are coming off their most impressive win of the season, and at 4-0, they’re one of only two undefeated teams in the NFL.

So why wasn’t Sunday’s marquee matchup against the Rams “flexed” into a prime-time game on NBC?

That’s a question many Niners fans have been asking over the past few days and it’s a query backed by sound reasoning. After all, Sunday afternoon’s game in Los Angeles pits a red-hot squad against the defending NFC champions in a game that has huge ramifications for the NFC West divisional race. It’s also being played in the nation’s No. 2 media market.

As for the game that NBC will be presenting Sunday night, it’s a matchup between the 2-3 Chargers and 1-4 Steelers. Not exactly must-see TV.

To understand why this happened it helps to know how the NFL flexible scheduling process works.

First, the NFL broadcast department generally must make a flex decision 12 days ahead of time so the networks can lock their travel and game plans into place. Look back two weeks on the schedule and you’ll see that the Chargers and Steelers posted lopsided victories over the Dolphins and Bengals, respectively.

The Rams, meanwhile, suffered an ugly 55-40 loss to Tampa Bay, and the 49ers had a bye.

I’m sure the NFL programming honchos are kicking themselves now, but at the time a ChargersSteelers matchup didn’t exactly look like dog meat. Since then, injuries have left the Steelers depending on a third-string quarterback.

Another factor: The NFL prefers not to overuse its flex moves early in the season. The league would rather save them for the second half when games with playoff implications become more apparent. That makes sense. You don’t want to waste all your bullets too quickly. And like any good drama series, you want to build your season to a crescendo.

Ironically, the NFL did flex out of the first Rams 49ers game last season. In Week 7, NBC went with a prime-time game between the Bengals and Chiefs that put the spotlight on the ascension of Kansas City’s scintillating rookie quarterback Patrick Mahomes.

The 49ers, at the time, were 1-5 and had lost quarterback Jimmy Garoppolo for the season.

I’m told that the NFL really has no limit on the number of flex moves it can make, but, again, the league doesn’t want to overuse them. It, of course, wants to spread the wealth around all three of its broadcast partners, including CBS and Fox.

The NFL launched its flexible scheduling system in 2006. Since then, the highest number of flexed games in one season is five (2015 and ’18). There have been seasons in which no flex moves were made (2014 and ’17).

As for the 49ers, they seem ready for their closeup. They’ve got two scheduled national prime-time telecasts coming — a Week 9 Thursday night game in Arizona (Fox), and a Week 10 Monday night clash with Seattle in Santa Clara (ESPN).

And you can bet that, if they keep winning, they’ll be flexed into more primetime action. Their Week 12 game against Green Bay at Levi’s Stadium appears to be a good candidate and maybe even the final regular-season contest against the Rams.