What had he learned about both himself, and his team, in its stunning run to the precipice of the NBA Finals a season ago?
"I learned about us, that we have a lot of young talent that can really play, play the right way, and we know how to win," Brown said.
"For me, what I learned about myself is that when I get put in the right position I can play with anybody."
Brown's comments were backed up by how he and his team handled that run -- one that came with both Kyrie Irving and Gordon Hayward sidelined with season-ending injuries. But while that run without two of Boston's All-Stars was supposed to be the thing that launched the Celtics to the top of the Eastern Conference this season, it instead has become one of the reasons people are now unsure they'll make it there.
"I think to some extent it's provided some uncertainty with roles a little bit," Hayward said. "When you have guys that are supposed to be your main guys get injured, and have serious injuries and miss a lot of time, then other guys step up and play well, you're going to have some uncertainty there. So I think that's how it has affected us a little bit.
"But we've kind of started to figure it out now."
Whether they truly have or not will help determine just how far Boston will go.
The Celtics -- to put it mildly -- weren't supposed to do what they did last season.
They lost Hayward six minutes into the season opener with a gruesome leg and ankle injury. Then, a year ago this week, Irving went down with what turned out to be a season-ending knee injury. Losing two All-Stars was supposed to be enough to sink them (and, really, should have been enough to sink just about any team).
"I still feel like they should've won that Game 7 and got to the Finals," Hayward said. "It definitely wasn't a surprise."
Though it might not have been a surprise to the Celtics, it certainly was to everyone else. It both made last season an undeniable success and saw the Celtics anointed as the favorites entering this season to succeed LeBron James atop the East.
"We believed in ourselves," Tatum said. "Nobody picked us to win any of the playoff series [we were in], but it's not about what the outside people say. It's about what we believe in this locker room."
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That belief, both in themselves individually and as a team collectively, helped power Boston's run last spring. But it also led to those three young players getting accustomed to far bigger roles than were planned for them. So when this season began, it proved difficult for them to suddenly shift back into the roles they were previously expected to fill.
Rozier went from being a full-time starter -- one who achieved cult hero status in Boston for his impressive assist-to-turnover ratio, "Scary Terry" nickname and calling Milwaukee Bucks guard Eric Bledsoe "Drew" during their first round series -- to Irving's backup again. Brown initially struggled as part of the starting lineup, and was eventually sent to the bench because of it. And while Tatum hasn't seen his role reduced, he hasn't been able to replicate the same highs he did in the playoffs -- including going toe-to-toe with James in the East finals.
"I think this is all part of growth," Celtics coach Brad Stevens said. "You're always in a different scenario every single year. Every year provides new challenges that all ultimately should make you better over the course of time.
"Those guys are still experiencing things for the first time. And, ultimately, last year provided a great deal of opportunity for them, and you saw the growth in the stage they were on. This year you don't see it as much maybe, but you should be getting better and you should be learning a lot.
"That's the part that, I told Jaylen, this will be as good of an experience as he ever has, when he looks back on it."
The Celtics will be hoping that's the case not only for Brown, but the rest of the team. And, at least recently, there have been signs of optimism that might be the case (even beyond the magical plane ride last week that the team claims has cured its ills).
Brown has consistently been one of the Boston's best players in 2019, and the combination of him and Hayward coming off the bench has gained traction in the past several weeks. Boston is outscoring teams by 5.3 points per 100 possessions when the two of them are on the court together.
Al Horford, meanwhile, looks like a completely different player after being slowed by knee tendinitis earlier this season, and he has been in the midst of one of his best stretches since joining the Celtics over the past several weeks. Irving is having arguably his best season as a pro on the court, and recently has vowed to stop going through the ups-and-downs that have followed him and the Celtics all season off the court.
"I don't really know what to say at this point," Brown said. "It is what it is. We're, what, 60-something games in? I'm just focused on getting to this year's playoffs.
"Last year was last year. I'm just focused on what's ahead of me, not what is behind me."
At this time a year ago, the Celtics were moving into uncharted territory. They were already without Hayward, had just lost Irving and seemed destined for a quick playoff exit without them.
Fast forward a year, and the Celtics remain in uncharted territory. Even with the struggles they've endured -- at least relative to what they were expected to do -- Boston still is in position to have a top-four seed in the East playoffs and accomplish all it was projected to.
And, if the Celtics can do all this, the difficulties that came with trying to make this work will all quickly fade this spring.
"We know what we're capable of, and we were close to getting to the championship [last year]," Tatum said.
"Now we're trying to get over that hump and get there."