Not long after the Boston Celtics won the NBA title in 2008, some new wall decor went up at their practice facility in Waltham, Mass.

It was a banner. An 18th one. But it stood out from the rest. It was completely blank, its story not yet written.

For well over a decade, that blank canvas showed that the Celtics’ most important championship was simply the next one. Players came and went, as did coaches, but Banner No. 18 was always there, even when the team opened up a new practice facility in Boston, the Auerbach Center, in 2018.

Suddenly it wasn’t just the Celtics who were constantly being reminded of the ultimate goal, it was the people of Boston, too. Thanks to the Auerbach Center’s 40-foot glass wall that nearly hangs over Interstate 90, commonly known as the “Mass Pike,” passersby could catch a glimpse of the blank banner in its new home.

Massachusetts drivers certainly didn’t improve their reputation with such a distraction, but with the banner on display daily, an entire state started to fully buy into the Celtics.

And it all ended up paying off.

Boston secured that coveted 18th title by beating the Dallas Mavericks in Game 5 of the NBA Finals on June 17, just two days before the six-year anniversary of the Auerbach Center opening its doors.

It had also been 16 years to the day since the Celtics went all the way in 2008.

Now Boston heads into the 2024-25 campaign as the defending champion, and it also finds itself as the betting favorite to go back-to-back.

However, that means nothing to Celtics coach Joe Mazzulla.

“I think the word ‘defend’ is a very passive-aggressive term,” Mazzulla said on the “Locked on Celtics” podcast. “You go back to the animal kingdom, some of the strongest animals don’t defend, they’re the most aggressive and they attack the most.

“… We’ve gone into a season not winning and we’ve gone into a season winning. At the end of the day, your mindset can’t change. You have to understand what goes into winning and losing, you have to understand the mental toughness that goes into it and you have to commit to the details on a daily basis.”

Among those savoring Boston’s 2024 title run the most are Jaylen Brown and Jayson Tatum, who went through plenty of trials and tribulations with the Celtics before getting their hands on the Larry O’Brien Trophy.

Brown, the No. 3 overall pick in the 2016 NBA Draft, and Tatum, selected third overall a year later, came up short in the Eastern Conference finals in two of their first three seasons playing together. Then they guided Boston to the Finals in 2022, but when they returned to the Auerbach Center that fall, a blank banner still was hanging for all of Massachusetts to see because of Stephen Curry and the Golden State Warriors.

Then came the 2023 playoffs, where the Celtics once again reached the Eastern Conference finals only to fall into a 3-0 hole against the Miami Heat. No NBA team had ever rallied from such a deficit in a seven-game series, and it was Brown who provided a rally cry for Boston.

“Don’t let us win tonight,” Brown said before Game 4, issuing a warning to Miami.

The Heat didn’t listen, and the Celtics went on to even the series to set up a Game 7 in Boston. History was never made, though, with the energy getting sucked out of TD Garden when Tatum rolled his ankle just 26 seconds into the contest.

Tatum was hobbled for the rest of the game, the Celtics never recovered and Miami punched its ticket to the Finals with 17 banners overhead.

Beating Dallas back in June made all of those ups and downs worth it in Tatum’s eyes, but the five-time All-Star realizes that Boston can’t take its foot off the gas. Last season was last season, and now the Celtics are back to square one.

“It was just an incredible feeling,” Tatum told Sports Illustrated. “Winning a championship, understanding all the hard work and sacrifice that went into making that goal a reality and understanding how it made you feel the night that you won a championship, the parade, all of it was worth it.

“And the unique part, and the cool part is, right now, it’s the start of the season, and we gotta start over. We gotta build it up from the ground and not look forward to June.”

In Boston’s front office, “2024 World Champions” now graces the lower half of an 18th banner that hangs in a glass case. Next to it is Banner No. 19. Blank. Patiently waiting to have its story written, too.

The Celtics might be back on top, but the message remains the same. The most important title is the next one. And if Boston plans to follow the ways of the animal kingdom, chances are it won’t be long until it has its sights set on Banner No. 20.