When Duke coach Mike Krzyzewski learned last summer that one of his former star pupils, Kyrie Irving, had requested to be traded from the Cavaliers, he was not stunned like many others were.

He coached Irving at Duke and with Team USA, and he knew there was some part of his game, some part of his style, that had yet to be fully unlocked. He sent Irving a text message in July, telling him that he was there for him if he needed anything. But Krzyzewski also knew that it seemed Irving knew exactly what he wanted.

Now, the coach steals glances of Celtics games whenever he can, watching both Irving and another former Blue Devil, talented rookie Jayson Tatum. He has seen Irving guide Boston to the best record in the NBA while making a career-best 47.6 percent of his shots. But the real impact, the coach said, cannot be measured in a boxscore.

“What I see happening with him right now is something I thought would happen eventually, and that’s him becoming a great leader,’’ Krzyzewski said in a phone interview. “He was born to be a great player, but he was also born to be a great leader, and I think that’s one of the reasons he wanted to take this chance.

“It wasn’t a negative against anybody [in Cleveland]. It was a positive of, ‘Look, I’m only going to do this for so long. I want to be that leader.’ And I applaud him for doing that. And he’s right. He was right in making that decision.’’

Krzyzewski is friends with Celtics coach Brad Stevens and team co-owner Steve Pagliuca, whose sons Joe and Nick played for Krzyzewski as walk-ons at Duke. After the massive August trade that sent Irving to Boston, Krzyzewski reached out to the Celtics.

“You’re going to see more from him than you ever saw in Cleveland,’’ he told them.

Krzyzewski said that with the Cavaliers, Irving had to adapt to playing with LeBron James. And he chuckled and said that if there is any player someone should adapt to, it is James, the best player in the world. But Krzyzewski knew how effective Irving could be when using various screens, and Cleveland’s scheme did not always afford him those opportunities.

“His passing,’’ Krzyzewski said. “A lot of people just started labeling him as a scorer. And I told the Celtics, ‘This kid is unbelievable in ball screens, and he can pass the ball.’ And I think you’ve already seen that, and that’ll only get better.’’

Last season 21.4 percent of Irving’s plays came in isolation situations, and that figure has dropped to 16.6 percent this year. Irving also has a 30.7 assist percentage this season. In three years alongside James he registered assist percentages of 23.6, 25.3, and 27.8.

Irving has been complimentary of Stevens and he has emphasized how much trust he has in his system. Krzyzewski said that’s evident just from watching Irving and seeing his interactions with his new coach. He said it is clear Stevens is allowing Irving to play with freedom and confidence, and that the two appear to be “a perfect match.’’

“I see it in their eyes and I see it in their actions,’’ Krzyzewski said. “Also, the fact that Brad is allowing Kyrie to lead in real time. That’s the best thing that can happen for a coach, where you have somebody on the court who’s leading while the game is going on. You’re not waiting for a huddle or whatever. That’s happening already, and that’s only going to grow.

“It’s a tremendous talent for a coach to have for a team, and a lot of people don’t have it. I’m telling you, real-time leadership while the game is going on, and I see it. It’s really neat to watch. I love watching how this is growing for them.’’

Irving’s growth has hardly surprised Krzyzewski. The first time he met Irving, when the point guard was just in high school, he told him he could become a point guard for the US Olympic team someday. Now, Krzyzewski sits in his office and looks at a picture of himself and Irving at the 2016 Olympics in Rio, with a gold medal draped around Irving’s neck.

“Look, I told him when he was a youngster, ‘You’re going to be one of the all-time best,’ ’’ Krzyzewski said. “You could just see it. I felt it, and that’s what he’s becoming. He’s becoming that.’’

After finishing that thought, Krzyzewski paused and chuckled. It was one thing for him to make such a gaudy prediction about a teenager nearly 10 years ago, and it has been another to watch it gradually become reality.

Adam Himmelsbach can be reached at adam.himmelsbach@globe.com. Follow him on Twitter @adamhimmelsbach.