The 49ers have a nasty habit in big games, and if they bring it to Las Vegas, their Super Bowl dreams will almost certainly become a nightmare.

No one can quite explain why the 49ers have posted slow starts in their four biggest games of the season — at Philadelphia, vs. Baltimore, and both NFC playoff games — and the good news for the 49ers is that it has only brought about one loss.

But the Kansas City Chiefs are a different kind of opponent.

Spot them an early two-score lead, and they will hold it until the confetti falls.

This season’s edition of the Chiefs is not a super team. Up to the start of the playoffs, it became trendy to write them off as Super Bowl contenders — for good reason: The Chiefs’ offense went from No. 1 last year (per DVOA) to No. 8 behind bad wide receiver play and even worse play from offensive tackles. Tight end Travis Kelce didn’t look like his All-Pro self all season, and Mahomes didn’t either. This team had taken a step back, and in the competitive AFC, that was perceived as tantamount to a death sentence.

And here’s the thing: There hasn’t been much improvement. Kelce might be playing better, but Kansas City still has so many of those issues heading into the Super Bowl.

The reason they are in the big game is because they are ruthless.

They might not have the firepower to beat any team they want anymore.

But in addition to one of the best defenses in the NFL, the Chiefs have the experience and knowledge to appropriately manage a game.

It’s all very reminiscent of the Tom Brady Patriots.

It’s become evident this season that the vast majority of NFL pundits are not, in fact, watching the full games. YouTube highlights, perhaps, but not the full game broadcasts or the All-22 film.

As such, the discourse (excuse me while I vomit) around Niners’ quarterback Brock Purdy is that he’s a dink-and-dunk game manager — someone who does very little but gets the ball to his playmakers on screen passes and lets them do the rest.

Meanwhile, Mahomes’ well-deserved reputation as a deep-ball-slinging, devil-may-care talisman persists.

In reality, the roles are completely reversed this season.

Kansas City is running the offense people think the 49ers run.

The 49ers are running the offense that people think Kansas City still runs.

Purdy was one of the NFL’s best and most frequent deep-ball passers this season. He was a gunslinger of the highest order.

Mahomes, meanwhile, has become a screen-pass merchant — his average air yards per throw was sixth lowest in the NFL this season.

That’s the way it had to be for Kansas City, though. Things had to be pared back — the offensive made more simple.

The Chiefs might not have the offensive firepower to beat you anymore, but they won’t beat themselves — they let their opponent take care of the rest.

That’s what Kansas City did in the AFC Playoffs. Miami playing in negative-degree temperatures made that playoff opener a breeze for Kansas City — the Dolphins made it clear from the opening snap that they’d do anything to get back to sub-tropical weather.

Then Buffalo beat itself the following week. The Bills scored with 3:23 to play in the third quarter of that game. They didn’t score again as their offense became solely predicated on Josh Allen running and throwing. He did neither at a high level down the stretch. One-man shows don’t work in the playoffs.

And then, in the AFC Championship Game, the Ravens went out and executed one of the strangest game plans in recent NFL history.

Kansas City scored 17 points in that title game. Had that been known before the contest, everyone would have fairly presumed the Chiefs lost.

But the Chiefs won because Baltimore quarterback Lamar Jackson — the most extraordinary running quarterback ever — decided to stand in the pocket for eight, nine, ten Mississippi on dropback after dropback.

The Chiefs’ opponents en route to the Super Bowl were not ready for primetime.

Are the 49ers?

This is the fifth massive game the Niners will play this year.

They’re 0-4 with good starts in them.

Against Philadelphia in Week 10 — remember how hyped that game was? — the Niners had negative offensive yards at the start of the second quarter.

Then, against Baltimore on Christmas, everything went wrong for the Niners on offense from the jump.

Green Bay never opened up a big lead in the teams’ NFC Divisional Round contest, but they held the Niners’ offense at bay in the battle of the Bays. The Niners needed a game-winning drive late in the fourth quarter to advance.

And then Detroit put a hurt on the Niners in the NFC Championship Game. If not for a Detroit meltdown that started late in the second quarter, and if not for a comeback for the ages — 27 unanswered second-half points — San Francisco would be watching the Super Bowl on TV like the rest of us.

Philadelphia, Green Bay, and Detroit all showed their own flaws after the Niners showed theirs.

But Kansas City won’t follow suit. This team — led by a Hall of Fame quarterback and head coach — has spent the last few weeks proving they can keep their poker face in Las Vegas.

The Chiefs have played enough playoff football to know that style points don’t mean a thing. You don’t get to skip a round if you blow out a team.

No, it’s survive and advance. The Chiefs might be more cunning than dominant this postseason, but the results are the same.

So, while the 49ers might feel pretty good about themselves (and for good reason) heading into the Super Bowl, after back-to-back comebacks, the better policy would be to play their best football early.

The last time these two teams met in the Super Bowl, Kansas City won with a late push. The 49ers led by 10 and had Kansas City facing a third-and-15 in their own territory with just over seven minutes to play in the game.

Then the Wasp stung.

But the Chiefs don’t hold those kinds of cards this time around.

That Chiefs team was a cobra. This team is a boa constrictor — simple, steady, and suffocating.

As such, a late-game push like the two that lifted the Niners to the Super Bowl is likely not in the cards for a third straight game.

The most important quarter of the Super Bowl might end up being the first.

And the Niners can’t afford to miss it.