WALTHAM — On a team that lacks real greybeards — those voices of reason that guide an NBA locker room, command attention, instruct younger teammates how to win and conduct themselves — the Celtics have had to embrace leadership-by-committee.

Maybe 20 years ago, teammates would discuss team issues in person, perhaps at someone’s home or in the team hotel. Someone would make a meal, the host would flip on their 40-inch analog television, and watch NBA highlights on “SportsCenter.’’ This was before NBA League Pass or TNT.

Nowadays, these Celtics communicate through group text messages. A core of veterans discuss team concerns and offer their forthright opinions on performances to improve team cohesion. So instead of face-to-face meetings, the players pick up their phones, send texts, and get feedback.

Call it “Chemistry — Millennials Style’’.

Celtics coach Brad Stevens doesn’t assign team captains. He doesn’t relegate leadership. That’s strictly up to his players and it seems they have understood the enormity of this season and formed a coalition to ensure their advancement and success.

The Celtics are 34 games into the season and their inconsistency has been maddening. But they’re in a jumbled Eastern Conference where the top seed is still available. They have to limit their stupors — such as losing consecutive games to the Lakers and Nets — and that is not lost on those leaders.

“Everybody on the team can just be a lot more vocal,’’ 11-year veteran forward Amir Johnson said. “Once you get one guy going, everybody kicks in and has their two cents, so it’s not just one guy. It’s a whole team effort. We all have a group chat; we might text late at night, ‘Let’s really lock in for this game.’

“We had a group message where we had like 15, 20 more games before the All-Star break, we said to ourselves, ‘Let’s try to get them all so we can have a good break.’ ’’

When team president of basketball operations Danny Ainge flipped the roster after the 2012-13 season and dealt away several veterans, he was able to acquire Gerald Wallace, who served as the “old head,’’ the voice of reason and discipline in the locker room.

With Wallace gone, the Celtics have had to compensate for the lack of leadership in different ways. Jae Crowder, in his fourth NBA season, has stepped into a more veteran role because of his vast improvement and contract extension.

During Monday’s 103-94 road win over the Brooklyn Nets, Crowder exhibited his vocal confidence and bravado by shushing the Brooklyn crowd after draining a 3-pointer that extended a late lead to 8 points. And he later flexed his muscles after bulling his way to a layup despite being fouled.

“I feel like I’m a key part of [the team’s emotion] and that’s on both ends of the court,’’ Crowder said. “I ride off my emotions. I try to control it for the most part. At that point in the [Brooklyn] game, we needed a play. My emotions run high.’’

There have been questions as to who would emerge as the most identifiable Celtics following the departure of Kevin Garnett and Paul Pierce. And it’s taken a couple of years for those players to emerge. Crowder has done so, as has Marcus Smart, who motivated teammates by forcing a jump ball with the Nets’ Donald Sloan when he dived for a ball that Sloan allowed to roll too long.

The Celtics are establishing themselves as a gritty team with workmanlike, no-nonsense players. Smart, in his second year, could eventually become the bona fide leader, but he has to remain healthy and productive.

“I think I do [consider myself a leader] and I think my teammates do, too,’’ Smart said. “Just by example. I try to go out there each and every night and bring the defensive intensity that I know we need and can have every night.’’

Leadership and accountability are critical elements for NBA teams. There’s a reason why the 76ers cut 20-year-old prospect Christian Wood in favor of signing 36-year-old veteran Elton Brand to serve as a mentor. And if there isn’t one central figure to serve as a mentor, players need to do it collectively.

The fate of the Celtics is in the hands of their players. They have to hold each other accountable and responsible for their triumphs and shortcomings. They have to teach each other professionalism and maturity, and if those messages come by the way of texts messages in capital letters, then so be it.

A text group may not be what the NBA management brethren would prefer, but if it fosters the progress of the team and builds cohesion, then it’s an innovative idea.

“We know where we are as a team,’’ Johnson said. “We’re inconsistent right now. We lose to some teams that we should beat, so I feel like this is the time we should really lock in and start getting these games in bunches.

“There’s a lot of room to improve. We’re definitely comfortable where we can yell at each other and take it as a positive thing. Ten years in you play to win the game and nothing else matters so any criticism, I’m there to take in and use it as fuel.’’

Gary Washburn can be reached at gwashburn@globe.com.