The phone rings at odd hours when you’re a sportswriter. Coaches and frontoffice personnel from other clubs sometimes are looking to trade information. On other occasions, they just need to talk.

Such was the case after midnight Wednesday when the leader of a Celtics rival in the Eastern Conference called. There was a pause after my reflexive, “Hello?”

“Are you (expletive) me?” he said.

This guy hoped his team would elbow its way into the Cavaliers-Celtics brunch at the top of the East, and now the arms race was making life more difficult for other teams in the firing radius.

Within a few minutes, he settled back and noted that both clubs still had a lot of work to do to build new team identities, more so the Celtics.

“Those are big-time talents with Kyrie (Irving) and (Gordon) Hayward, but it’ll be interesting,” he said. “Everyone’s going to be watching what Boston does right out of the gate, but they might not have it all together right away. They’ve still got a lot of young guys who have to play really big roles. I’ll be more concerned with how it all blends when you get to next February and March and, you know . . .”

You know, the playoffs.

Such greater concern for the latter portion of 2017-18 is well founded. With just four players — Al Horford, Marcus Smart, Terry Rozier, Jaylen Brown — remaining from a 53-win team, it is nigh impossible to have any kind of real continuity. In dealing away Isaiah Thomas and Jae Crowder on Tuesday for Kyrie Irving, the Celtics didn’t just lose their specific talents, they lost their team personality. And let us not forget Avery Bradley in this equation.

If asked to define the Celtics of recent vintage, you’d point to the unwillingness/inability of people like Bradley and Crowder to back down on defense and what that communicated to those like Smart who came off the bench. Then you’d note the same quality on offense in Thomas, and even people employed by the team were admitting they were stealing some games on attitude and chemistry.

Indeed, Thomas was and is a brilliant scorer. The way he worked in the summer of 2016 to improve his game after an All-Star season should be an inspiration to aspiring bucketeers. Attitude as much as aptitude made him a fourth-quarter phenom.

And Horford was a talented, veteran rock who made last year’s foundation more able to stand up amid the playoff storms.

So now the Celts have more acute individual talent in Irving and Hayward. They can better score in isolation (in Irving’s case, if only because at 6-foot-3 to Thomas’ 5-9, he can get his shot off over more defenders) and take advantage of defenses leaning the wrong way. Remember, when Bradley went to the Pistons and was asked the toughest player for him to guard, he immediately replied that it was Irving, adding that it was “not even close.”

We know what Irving can do on the court. There are NBA Finals highlight videos to prove it.

But his greater test here will be more spiritual. His talent and standing as an NBA champion will require him to lead. Coach Brad Stevens has done away with captains, but Irving has to set the tone and see the larger picture in every situation.

On the floor, he has to make sure people get the requisite amount of touches so they are prepared to make big shots if called upon late in the game. Off the court, he has to take advantage of the opportunity to write the public narrative. Irving has to smooth the waters when the media gathers around him in the wake of a tough loss, knowing that what he says will be atop the reports disseminated. And he has to spread the affection when things are going well.

From what I’d been able to gather in the immediate aftermath of Irving’s trade request becoming public (and maybe NBA commissioner Adam Silver can appoint a special counsel to investigate how that got out; I’m guessing you’ll find some interesting fingerprints), this wasn’t all about Kyrie wanting to be the proverbial “man.” He didn’t necessarily mind playing beside the most talented player in the game and being No. 2 in the Cleveland galaxy. Irving just didn’t like LeBron reminding him of that fact every 20 minutes.

Now Kyrie essentially has the James role. He has the chance to show he is a benevolent leader who will talk with more sincerity about “the team.” And this is critical on a Celtics club that will need relative children like Brown and Jayson Tatum to make major contributions.

How well Irving builds confidence in others will be hard to define with analytics, but it will rank in import with his points and assists.

And it will be a major determining factor in whether NBA coaches are relaxing late at night or picking up a phone.