The rest of us had doubts, but it seems these Celtics knew how good they could be all along

I had ‘em for 44 wins and the play-in. You?

Be honest now. Save for the random eternally-hopeful diehard, the only people who thought the Celtics could approach this — winning 56 games, earning the second seed in the Eastern Conference, and having a small but legitimate chance of collecting Banner 19 come June — were the people who went out and made it happen.

After all, the Celtics were coming off a season that ended with a six-game loss to the Knicks in the second round, a series in which they lost so much more.

Superstar Jayson Tatum suffered a torn right Achilles tendon in Game 5 while lunging for the ball. Their hopes of repeating as champion ended with agonizing abruptness, and it seemed their chances of winning a title in the near future did too.

Suddenly, the recurring term of the offseason was “gap year.” With Tatum certain to be sidelined for months, if not the entire season, Celtics management took the logical step of resetting their luxury tax repeater penalties, which meant resetting a chunk of the roster.

Al Horford, Jrue Holiday, Kristaps Porzingis, and Luke Kornet — important and beloved members of the ’24 champs — moved on. The less accomplished Anfernee Simons, Luka Garza, Josh Minott, and 19-year-old first-round pick Hugo Gonzalez came aboard.

A gap year. Sure looked that way, especially when it didn’t start well. The Celtics lost their first three games, including an opening-night loss to the 76ers when they blew a late 9-point lead and rookie VJ Edgecombe dropped 34 points on their heads in his NBA debut.

Those first three games? Who knew then that they would be the low point, and that most of the issues that ailed the Celtics early — especially rebounding — would become strengths?

Which brings us back to the people who went out and made it happen.

They include president of basketball operations Brad Stevens, who certainly is appreciated for his extraordinary work in finding the ideal, often unheralded players to fit the Celtics’ close-knit, team-first culture, yet is somehow underrated given the degree of difficulty of building and maintaining a competitive roster.

Remember this for the offseason, whenever it comes: When Stevens signs a player, try to figure out what the front office likes about him and how he might fit. Because there’s an excellent chance that player will become a fan favorite before you know it. Even Simons and Minott, both of whom are playing elsewhere now, won over Celtics fans during their time here, especially the former.

Other people who believed? Of course that includes coach Joe Mazzulla, who was giddy in his endearingly odd way at the chance to shut up doubters. Derrick White told a story on his “White Noise” podcast about Mazzulla calling him over the summer, wishing him happy birthday, telling him “everyone thinks we’re going to [stink],’’ and immediately hanging up.

Mazzulla may not want the Coach of the Year award, but had better win the thing. One of this Celtic team’s superpowers is how every player right on down the bench — from Garza to Jordan Walsh to Ron Harper Jr. — is ready for his opportunity, even if he hasn’t seen meaningful minutes in a few games, or even weeks. Having players prepared and ready to contribute — or even thrive — when their moment comes is the ultimate reflection of a coach.

One of the reasons Mazzulla shuns personal accolades is that he genuinely believes credit must go to his players, since they’re the ones doing the work on the floor. No Celtic deserves more praise than Jaylen Brown, who savored the chance to prove he could be the leading man in a fulfilling basketball story. Brown averaged 28.7 points, 6.9 rebounds, and 5.1 assists, and while he’s not going to fulfill those frequent “M-V-P!” chants at TD Garden, he is more than deserving of first-team All-NBA.

Brown has had plenty of support from Quintessential Celtic Derrick White — that’s his legal name now, I checked — as well as Payton Pritchard, who leveled up as a scoring threat to the point of being occasionally unstoppable. Tatum returned on March 6, and while some of his explosiveness has yet to return, he’s essentially looked like himself, which seems like a miracle but is a tribute to science and his hard work. His rebounding and passing have been nothing short of exceptional.

The staggering improvement of Neemias Queta into an above-average starting center — one who has developed far better awareness on both ends of the court — is on the short list of the most important plot twists this season. And who saw Baylor Scheierman becoming an entertaining and effective Swiss Army knife of a role player?

I mean besides those who put this team together, coach it, and play for it.

Just about any outcome this postseason is plausible, and I mean that mostly in a positive sense. The Sixers could be trouble in the first round if Tyrese Maxey goes off, but it’s not worth sweating now. A bout with this Knicks in the second round would go the distance, but I like the Celtics’ chances of avenging last year’s outcome.

The Celtics absolutely can get to the Finals. I believe they will, and at the least, should not be underestimated against the winner of the West.

The Celtics are a joy to watch, and a truly outstanding team. They’ve proven that from Game No. 4 on.

Just how good are they? You and I are about to find out.

The Celtics themselves? They already know. It seems they have all along.

Chad Finn

Sports columnist

Chad Finn is a sports columnist for Boston.com. He has been voted Favorite Sports Writer in Boston in the annual Channel Media Market and Research Poll for the past four years. He also writes a weekly sports media column for the Globe and contributes to Globe Magazine.