WALTHAM, Mass. – During his first two professional basketball seasons, Colton Iverson has been chomping at the bit to earn an NBA-level reputation. He’s yet to make a regular season roster in the NBA, but the 7-foot center is willing to take any road that will get him there.

The Celtics originally acquired Iverson from the Indiana Pacers during the 2013 NBA Draft. The 53rd overall pick then journeyed overseas to Europe, where he has been developing his game during the past two seasons.

Now, the 26-year-old is in the midst of his third summer league session with the C’s, and the organization has noticed some positive changes in his game.

“We had him right out of college and each year he’s come back, he’s added things to his game,” Celtics assistant coach Jay Larranaga said Thursday afternoon, following summer league practice. “He’s always been a great guy to have on your team, great guy to be around, but he’s become a pro and understands what it takes to improve.”

Larranaga believes that during Iverson’s time in Europe, “He’s made a step up and has gotten better and better, and he’s demonstrated that, at least in these first two days [of summer league workouts].”

He seems like a completely different player, according to Larranaga… for the most part, at least.

“He’s still huge, so that has remained the same,” said the assistant coach with a laugh.

That size is what shapes Iverson’s game; he hopes the C’s find a use for him and can somehow fit him into their mold.

“I’m physical, I’m a presence in the lane, I’m a defender and I do the dirty work that people don’t like to do,” said Iverson. “I think every team needs a guy like that.”

While he thrives as a powerful presence in the paint, Iverson said he’s been working on slimming down so he can keep up with smaller, more agile players.

“I’ve [gotten] quicker,” said Iverson, who currently weighs 252 pounds. “I’m just more mobile. I’m not slow like I used to be and I think it really shows.”

During his 2014-15 season with Laboral Kutxa Baskonia of the Spanish League, Iverson averaged 7.2 points and 5.9 rebounds – including 2.4 offensive boards – per game. That’s not bad, considering the fact he only played 20.5 minutes per contest.

The biggest lesson that he’s learned since turning pro is that, “I’ve got to be more demanding. More demanding of the ball, more demanding of rebounds; that’s what gets you to the next level, and I think I did a better job this last year in Spain.”

He’s hoping his progress will get him to the highest level, but he’ll have to prove himself this summer when the Celtics take the floor in Salt Lake City and Las Vegas.

“I know it’s going to be tough again to make the roster,” said Iverson, who turned 26 on Monday. “There’s a lot of players on contract right now and it would take some moves to happen.”

Regardless of how the summer league goes for Iverson, he will have something to celebrate following the hectic grind: At the end of July, he plans to marry his fiancé in Minnesota.

After that, he’d love to hitch a ride to Boston to tie another knot.