The Celtics guard said the veteran leadership of James when they were Cleveland Cavaliers teammates was something that enabled him to grow.

BOSTON – He entered the NBA as the top pick in the 2011 draft, joining a team going through a painful transition.

Kyrie Irving was 19 years old when he joined the Cleveland Cavaliers, a franchise that was a year removed from losing LeBron James via free agency to the Miami Heat.

He had played only 11 games in one year at Duke because of an injury and now was joining a team desperately looking to get off the ground following a 19-win 2010-11 season.

So did Irving consider himself the face of the Cavaliers as a young player learning about the NBA on the fly?

“I mean, I wasn’t the face of the franchise,’’ said Irving. “They made that very clear. I was just a great piece in Cleveland, which I gratefully accepted.

“I was just a great piece. They weren’t giving me the keys to the franchise. I was too young, man. I didn’t deserve them. But after a while, I felt like I earned it and I took a lot of that responsibility on myself, still wasn’t ready to do it.’’

The Cavaliers won only 21, 24 and 33 games in Irving’s first three seasons before the return of LeBron changed everything.

The team went to the NBA Finals three times with Irving playing alongside James, winning the title in 2016 thanks to Irving’s last-minute 3-pointer against the Golden State Warriors in Game 7 on the road.

Irving famously requested a trade out of Cleveland in the summer of 2017, though, reportedly unhappy with playing in the shadow of James, and he landed with the Celtics.

Now, the 26-year-old Irving is clearly the top player on a team expected to reach the Finals next June, and last week, he announced his intentions to re-sign with the Celtics next summer.

Prior to practice at the Auerbach Center on Tuesday, Irving, who has spoken very little about the split with the Cavaliers, offered praise for James while discussing how being with the best player in the NBA helped his career.

“I honestly just saw it as a point in my career where I needed to learn and grow,’’ said Irving, who returned to practice after being sidelined with sore ribs. “I took as much knowledge as I could and I moved on with my career. From that point, I think I learned a lot about myself and how much of a competitor I am.

“I think the biggest thing is when I see the young guys we have here, and I’m a young guy myself, I had to learn a lot about the game of basketball. Being with LeBron and Mike Miller and James Jones and being around the veterans like that (helped).

“Being around them with the basketball knowledge was something I needed. I was a fourth-year (player), just signed a $90-million contract, I’m thirsty for everything. I was taught just roll out the ball and go play. That was the first time I had to watch film, be ready for the playoffs, learn what it’s like to be competed against rather than competing.

“I learned a lot from that point to be in this position now.’’

The Celtics made it to Game 7 of the Eastern Conference finals last season without Irving and Gordon Hayward, so expectations are high going into this season, which starts Tuesday night against the Philadelphia 76ers.

After taking two days off, the Celtics were back on the practice floor for the first of six days of practice. They struggled through a 1-3 preseason, looking shaky at the defensive end, and now must fix the problem areas.

Irving knows that young players like Jaylen Brown and Jayson Tatum are going to have to adjust to the role of favorite like he did when James rejoined the Cavaliers.

“I became the hunted, and that’s the biggest change you’re going to see,’’ said Irving. “Our effort has to surpass other team’s talent and effort at times.’’

Irving, who played only two preseason games, said the Celtics will have to figure out how to play together before everything comes together. They are getting Hayward in the mix again after he played less than one quarter of one game a year ago.

“Making their jobs a lot easier and making the game a lot more fun for our wings and everyone else is part of my job as well,’’ said Irving. “It’s showing them and helping them as much as I can to learn about the game of basketball. It’s art, making reads on the fly. It’s a step by step process. It’s going to take time. We’re aware of that.’’

Smart punished: Marcus Smart was hit with a $25,000 fine but no suspension for his confrontation with J.R. Smith on Saturday night in Cleveland.

“I wasn’t surprised. I figured something was coming. I didn’t know exactly what it was,’’ said Smart, who reacted after Smith pushed Aron Baynes.

“That’s how I’ve always been. That’s me. Nothing’s going to change, nobody’s going to change me. It’s me being me. It’s how I was raised. (But) I’ve got to think about the team. My teammates need me and I can’t be missing games.’’