The Boston Celtics are running it back. In fact, they may just be running it back harder than any team in the last 20 years.

With the singing of Sam Hauser to a four-year, $45 million contract extension on Sunday, the Celtics have now guaranteed that their entire championship top-nine will be returning for at least next year. And as far as I can tell, that’s the first time in at least the last twenty years that has happened. I couldn’t even find a championship top-eight staying intact, let alone a top-nine.

That is pretty much unprecedented, and it’s worth wondering if that’s actually a good idea. It’s also more worth wondering if they really had a choice, and the most worth wondering if it even matters right now. I’m like 91.2 percent sure it’s a good idea, but let’s play out all the various situations the Celtics have now gotten themselves into and see if we can figure it out. Break.

Just so we’re all on the same page: Jayson Tatum, Jaylen Brown, Derrick White, Jrue Holiday, Sam Hauser and Payton Pritchard are all signed for at least the next four years, which is absolutely insane when you say it out loud. Kristaps Porzingis is under contract for the next two, and Al Horford will be an unrestricted free agent next summer, as will Luke Kornet.

That is the Celtics’ entire relevant rotation. They are likely to lose Oshae Brissett to free agency, a marginal contributor last year, but retained Xavier Tillman who basically subsumed Brissett’s role in the playoffs. He was particularly effective in spots in the NBA Finals, meaning that — for all intents and purposes — the Celtics are basically keeping their top-ten.

Let’s start with the fun stuff. That’s awesome, this is awesome, I love this, you love this, everyone loves this. These contracts are way more fun than last summer, which was the unfortunate media feeding-frenzy around the Jaylen Brown extension, at the time the richest contract in NBA history. It’s not that Celtics fans didn’t like the contract; most of us loved it. But none of it tasted as sweet as it should have coming off a crushing Eastern Conference Finals defeat.

But after winning the NBA Finals, this offseason has been dipped in so much Nutella, powdered sugar, and topped with so many strawberries and cream that we’re basically making a 5-year-old’s ideal IHOP order. Everything is inherently awesome, backed up by the endless sunshine and lollipops of winning the NBA Finals. Kornet one-year deal? Epic. Tillman coming back? Spectacular. Derrick White and Jayson Tatum extensions on the same day?! Someone set up another Duck Boat parade.

Depending on where you stand on the Official Celtics Love/Hate Spectrum — with “1960s Los Angeles Lakers Fan” at one end and “50-Year Celtics Season Ticket Holder” on the other — you’ll probably see the flurry of extensions dramatically differently.

At the positive end, the Celtics just won the NBA Finals and are going to be the favorites to win it again at the very least through November. When healthy, they are the best team, and while the Eastern Conference has improved, it’s not exactly prime LeBron James arriving in Miami to subjugate the conference like some sort of morally-depraved 16th Century Conquistador, like he did in 2010.

Let’s take stock: the Milwaukee Bucks are basically the same, but Giannis Antetokounmpo does still definitely exist. Paul George is now on the Philadelphia 76ers, which doesn’t guarantee them anything but does make them a lot better. Mikal Bridges is now on the New York Knicks, apparently looking to prove that reconstructing a college championship team in the NBA is the league’s best-kept secret. Again, nothing is guaranteed, but they are also better, which is the goal of teams that think they have a chance.

The radical Celtics positivist would argue that none of those teams actually have a chance, which I would argue is probably a little too much powdered sugar. Strength invites challenge, and the rest of the Eastern Conference wasn’t just about to fold in the face of a Celtics roster that, on paper, is absolutely cracked and isn’t going anywhere.

The 1960s Lakers fans among us will probably focus less on the quality of the roster and more on the absolutely bananas financial situation this is going to put the Celtics in. In 2025-26, once all those extensions kick in, the Celtics will be running by-far the highest payroll in NBA history, and almost certainly will be going over the NBA’s most-recently-established salary cap boogyman for two straight years: “The Second Apron.”

I don’t want to dwell on finances too much, since the practical implications of this newfangled device — invented last offseason to prevent overpowered superteams from existing — haven’t yet had time to play out, but here’s the upshot. Because the Celtics will be exceeding a super-high number in the luxury tax twice, they will only be able to make minute roster changes; limited to the veteran minimum, first round and second round exceptions. Their first round pick will also be moved to the end of the first round.

There has been lots of speculation about how teams view this “Second Apron,” most of it saying it’s basically the NBA’s fancy version of a hard cap, intended to basically save the owners from themselves by providing such a colossal disincentive to overrun the luxury tax that nobody would do it. Let alone twice in a row.

Well… it seems like the Celtics are going to do it. Whatever agreement Brad Stevens and Wyc Grousbeck have behind the scenes seems to boil down to “sign everybody regardless of consequences and then figure it out later.” By doing so, their roster flexibility is basically zero, which — so long as everything remains sunshine and lollipops for the next few years — shouldn’t matter.

This assertion is the 8.8 percent that scares me. Everything looks awesome now, but stuff tends to go wrong in the NBA, no matter how great everything might look on paper. Teams have gone all-in, built superteams, and flamed out so spectacularly that people are left wondering if the Brooklyn Nets should just move back to New Jersey.

I’ve quoted former Celtics assistant Jay Larranaga many times as saying to Brad Stevens, “If we’re not trying to improve, we’ll stop being good,” as I truly believe that remaining aggressive is the key to not getting passed by. But I take solace in the inevitability of it all, because what were the Celtics going to do? NOT re-sign the historically great team that just won the NBA Finals?

Whether or not this will wind up backfiring is a moot point, and it’s probably less likely than other financially-hamstrung teams. The Celtics have not achieved this quote-unquote superteam by trading draft picks. Their hardships are financial, not material, and whomever Grousbeck ends up selling the team to will know the situation they’re getting into. Also, if the Celtics have to trade someone in order to get under the Second Apron if things go sideways, then it will be a good thing since… you know, things have gone sideways.

Seneca the Younger said that a man who suffers before it is necessary suffers more than is necessary. When things are going well, we may as well just bet on them continuing to go well rather than freaking out about a yet-realized future. And for now, I choose to eat the 5-year-old IHOP breakfast.