The Eagles’ toughest playoff opponent won’t be the 49ers or Rams or Seahawks. It’ll be themselves.

Is anyone on or around the Eagles having any fun? It doesn’t seem that way. It hasn’t seemed that way all season. Sure, Jordan Davis has a personality as big and buoyant as he is, and Brandon Graham’s return from retirement has brought some effervescence back to the locker room. But on the whole, things have been pretty dour, or at least kind of grave and serious and humorless, for a team that’s coming off a championship.

The examples are everywhere. Jalen Hurts has won a Super Bowl, was named the most valuable player in that Super Bowl, plays his best in the Eagles’ most important games, and has a smile that would stop a beauty shop. Yet in public, he often has a demeanor that suggests that, if he so much as grinned, his face would split open down the middle. Before he left the lineup because of his foot injury, Lane Johnson had not spoken after a game since the Eagles’ loss to the New York Giants on Oct. 9, when he called out the team’s offense for being “too predictable.” Not exactly Once more into the breach, dear friends stuff.

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Hurts’ relationship with A.J. Brown has been a source of speculation and tension for months. Brown has made his feelings about getting the ball — or, more accurately, not getting the ball — plain on social media, and his complaints sparked a ridiculous discussion about whether the Eagles might/should trade him in the middle of this season. Adoree’ Jackson and Kelee Ringo have, at various times, been considered the single worst cornerback in team history, as if Izel Jenkins, Nnamdi Asomugha, or Bradley Fletcher had never lined up against a decent receiver and immediately been burnt like toast. And if you want to be the ultimate Debbie Downer at a friendly get-together, just say the words Kevin Patullo, and you’re bound to start one of the partygoers ranting like a wing nut online influencer. Hell, your house might even wind up covered in egg yolk.

The point here is not to suggest that the Eagles have been beyond criticism. Of course they haven’t. The point is that their entire season has felt like one of their offensive possessions. It has been a generally joyless slog that, even when it leads to a good outcome — a touchdown, a victory, a second straight NFC East title — hasn’t inspired much optimism or hope that the team will repeat or sustain that success.

You don’t need to be a gridiron genius or a Philly sports sociologist to understand why. There are plenty of cities and markets where, if a team won a Super Bowl in the manner that the Eagles did last season — winning 16 of its final 17 games, dominating the conference championship game and the Super Bowl itself — the celebratory buzz would last for years. Championship? Who needs another championship? We just won one! That backup long-snapper never has to buy a drink in this town again.

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Philadelphia is not one of those cities or markets. Here, winning is the most addictive of drugs, and when it doesn’t happen, or when it doesn’t happen in the most satisfying manner, the entire region goes into a collective withdrawal, and a more powerful hit — a higher high — is required for everyone to level off.

From Eagles fans to the players themselves, there has seemed to be an ever-present blanket of expectations weighing on them. It’s as if the only thing that would make anyone happy and relieved at any moment this season would be another Super Bowl victory — a benchmark so lofty that it virtually guarantees people will be worried at best and miserable at worst unless the Eagles win every game 49-0.

The one person who appears to acknowledge this dynamic, and appears to be fighting against it, is Nick Sirianni. He has spoken since the middle of last season about his attempts to “bring joy” to every practice, every game, every day of work, as if to lighten the burden that his staff and players were bearing.

“In professional football,” he said recently, “there are all these pressures, these ups and downs and everything like this, but we got into this game because we loved it. I think that’s a really important thing. In the world, you can let things beat you down a lot and not really give knowledge to all the things you have going on that are really good.”

Hanging on a wall in Sirianni’s office is a photograph of him and his three children. The photo was taken after the Eagles’ 20-16 victory over the Cleveland Browns last season — the game after which Sirianni brought the kids into his postgame news conference and was criticized bitterly for it. I did some of the criticizing, and I stand by it. The gesture was silly and tone-deaf at the time, mostly because the Eagles were 3-2 and playing terribly and Sirianni’s career-dissipation light was flickering. No one was about to give him or them the benefit of the doubt then.

But now that they have won a championship, it’s easier to see that moment as part of a continuing effort by a head coach to keep the pressure of meeting that standard from crushing his team. In that way, the Eagles’ toughest opponent in this postseason won’t be the San Francisco 49ers or the Los Angeles Rams or the Seattle Seahawks or whatever team they meet in Super Bowl LX if they happen to make it that far. Their toughest opponent will be, and has been all along, themselves.