John Holland’s five-year journey to the NBA, an unlikely scenario for an unheralded player from a mid-major school, began with an unusual midseason meeting with his Boston University coach and his parents in January 2011.

Such conferences to include a player’s parents are rare. But then-BU coach Pat Chambers needed to address his senior forward.

“We were not playing well; we were not playing up to our capability and he was a leader and he wasn’t leading us to his capability,’’ Chambers said. “It turned a lot of things around for everybody. For John, for our team, the direction of where we wanted to go and it’s something that had to be done. The greatest gift you can give anybody is the truth and during that meeting the truth was told, and he turned everything around.

“Five years later, look at him.’’

The Celtics signed Holland, who was playing for the Canton Charge of the NBA Development League, to a two-year contract Tuesday. It is his first time on an NBA roster during the regular season, culminating a long sojourn that took him to France, Spain, Turkey, and Ohio.

Holland was a four-year player at BU, leading the Terriers to the NCAA Tournament as a senior with a brilliant second-half performance in the America East tournament final against Stony Brook. He carried NBA aspirations, but like hundreds of college players whose eligibility expires, Holland went undrafted and therefore had to take the arduous road to the highest level.

“You have no choice but to believe [you can make it to the NBA]; of course I believed it could happen,’’ he said, dripping sweat after a pregame workout. “That’s what you’re down there for. When I signed up [in the NBADL], I signed up knowing I could play at this level, just hoping I’d get the opportunity. When I got the call from the Celtics, I’m just happy to do whatever I can, be a good teammate and just do whatever I can to help the team win. They’ve done a great job for 80 games, you know?’’

Holland received more exposure playing for Canton in the NBADL this season than he would have gotten playing overseas. There is a heavy price to play in the D-League for NBA hopefuls. They get to play closer to home, but the salaries are considerably lower, the cities smaller, and the venues half-empty.

Holland averaged 16 points, 3.1 rebounds, and 2 assists for Canton, and he led the Charge to a first-round playoff series win over the Maine Red Claws, the Celtics’ affiliate. He seemed honestly surprised at his promotion.

“Money is good [overseas] but sometimes it is about the dream,’’ Holland said. “You have a dream ever since you start playing basketball to play at the highest level and that was always my goal, to play at the highest level I can. I didn’t know what that was. If it was overseas, it was overseas. I had to give it a try. I went overseas for four years, so I figured I’d really give it a try and stick it out and I’m just happy that it worked out.’’

Chambers only coached at BU for two seasons before being hired to resurrect the Penn State program. But he has kept in touch with Holland since they both left BU following the 2010-11 season. What’s more, a sleeping Chambers received a phone call at about 10:30 p.m. Sunday night.

It was from Holland. He was headed to back to Boston, this time as an NBA player.

“It just says a lot about his determination, his attitude, and his perseverance,’’ Chambers said. “Here’s a kid who had a dream. We talked about it after 2011. We talked about agents and he looked at me in the eye and said, ‘I want to play in the NBA.’ He never lost that hope of making it one day. It’s just an incredible story.’’

While at Penn State, Chambers also coached Tim Frazier, the workhorse point guard who has been feverishly working to stay in the NBA the past three years. Chambers has coached hundreds of kids who say they want to play in the NBA, but very few succeed. Sometimes they aren’t good enough. Sometimes they get discouraged by the odds. Sometimes they lose their love for the game.

What stands out for Chambers about his relationship with Holland, which took time to develop, remains that conversation five years ago when the Terriers were reeling. That team began the season 10-13 and had just been pounded at New Hampshire when Chambers decided to pull Holland aside. BU did not lose again until the NCAA Tournament to Kansas, a game the Terriers trailed by just 4 at halftime before falling, 72-53.

Holland scored 19 points against NBA-lottery picks Markieff and Marcus Morris. His transformation convinced Chambers that his NBA goal was attainable.

“Once we had that conversation, we won the next 11 games and he thrived as far as everything I was asking him to do,’’ Chambers said. “Again, that’s a guy who’s a young adult and I’d like to think my staff and I helped him become a man and a leader. I am so proud of him.’’

Holland had a little trouble remembering that meeting, considering his plethora of basketball experiences the past five years. What does stand out is his frustration toward the end of his senior season, and his desire to change his fate.

“It was a combination of the season coming to an end and my career coming to an end, basically, and not really having won anything,’’ Holland said. “From what I remember, [the conversation] was good. I think it’s something that just basically put everything in focus and got the goals straight.’’

Gary Washburn can be reached at gwashburn@globe.com. Follow him on Twitter @GwashburnGlobe.