It was a move suited for the NBA’s most experienced players, those who have been around the league long enough to sustain an unwavering sense of poise in the most urgent moments.

As Rajon Rondo elevated, he blindsided LeBron James and dished a behind-the-back pass to Tony Allen mid-air, pulling off the jaw-dropping move with a quiet veteran calm. Rondo looked like he had been dominating the court for years. The reality is, though, it was just three seasons ago that he was looking to establish himself on the floor.

It has only been four years since the Boston Celtics made a trade with the Phoenix Suns to land a 20-year-old point guard from Kentucky with he 21st pick in the 2006 NBA draft. While the Celtics personnel saw talent, critics saw flaws. His lack of offense was ripped apart and his attitude was questioned. The early consensus on Rondo’s game was more problematic than promising.

“First [time I saw Rondo] was on film and I said, ‘Jesus guys, this guy can’t shoot.’ I was like, ‘He’s going to be terrible.’ I did,” Doc Rivers recalled to WEEI.com. “You saw the instincts, but just his shot being where it was at, I was thinking, ‘Wow, there’s no chance.’

“But then you could see when he came into the gym, you saw him personally and you said, ‘This kid’s different. He has a chance,’ because his basketball IQ was so high as a young player. He’s stubborn as hell, but you have to be a little stubborn if you’re smart. Then I thought there was a chance. Then we started working with him and you could see he was willing to work, I thought he had a chance to be really good.”

For those who played with Rondo on the 2006-07 Celtics squad, his remarkable performance in the 2010 postseason is not surprising. They saw early on that the rookie had the potential to play up to star level.

There are three attributes mentioned repeatedly among the teammates who offered their first impressions of Rondo -- ball handling, quickness, and intelligence. They were instinctive to Rondo, and even though he had a lot to learn about NBA basketball, these natural abilities set him apart early on.

“When I first saw him I knew he was very athletic, a great passer, very high IQ,” said Kendrick Perkins.

Sebastian Telfair added, “I remember him having these long arms. I was like, ‘Man, he’s got the longest arms I’ve ever seen.’ He has the ability to pick up the ball 94 feet with those long arms, being so fast and being so quick. It was one of the things that I was like, ‘He can dominate in this league with those qualities.’ ”

Rondo began his rookie year as the backup point guard to Telfair. He suited up with the second squad during practice drills, where it was his job to challenge the starters' defense. It was during that time that Brian Scalabrine first recognized his potential.

“I thought he was special,” Scalabrine said. “One drill that we used, Doc used him in a pick-and-roll drill, as in our starters need to stop him. … Literally, he could do what he wanted. He pretty much was scoring on three of our guys, or making the right play, or dumping it off, or getting to the basket. This is a pick-and-roll league, and for a player to be that good at the pick-and-roll is just amazing for us to get him where we got him.”

Offense in practice drills did not translate to the court, however. Rondo was always a defensive-minded player and he struggled at the basket, shooting 41.8 percent from the field and averaging 6.4 points per game. Opponents purposely left Rondo open, inviting him to shoot while rotating toward his teammates, including Celtics top scorers Paul Pierce and Al Jefferson. He made less than 200 field goals the entire season.

But Rondo faced a bigger challenge than hitting his shot. While Rivers believed Rondo was affected by his scoring struggles, there was a larger issue for someone who is tasked with being the floor leader. One teammate recalled Rivers, a former point guard himself, and Rondo did not always see eye-to-eye on running the floor, as the rookie often tried to assert his own opinion.

“I thought the shooting part of it was big for him, and then I thought just listening and trusting,” Rivers said. “The first 25 games he didn’t play much because I don’t know if he didn’t trust us, didn’t trust his stuff. And then once he let us in, I thought that allowed him to move forward.”

Rondo started his first NBA game on Feb. 2, 2007. He recorded 23 points, six rebounds and six assists in a commanding win over the Los Angeles Clippers. He started the following three games and eventually got the nod in 21 of the final 22 regular-season games.

Rondo averaged 10.6 points, 5.4 rebounds, 5.8 assists, and 2.4 steals in 36 minutes over 25 games as a starter. In contrast, he averaged 4.5 points, 3.0 rebounds, 2.9 assists, and 1.3 steals in 18 minutes during 53 games off the bench.

As his minutes increased, so did his leadership.

“It developed tremendously,” said Leon Powe. “As he started gaining more confidence and getting more minutes, coach started to put him in a little bit more, started to trust him a little bit more. Stuff started to click and you could see he had the characteristics of running the team.

“He knew where everybody was supposed to be at once, and I was like, ’That’s amazing for a young player.’ He knew how to talk to everybody. If somebody was getting mad in a game and getting hot, he calmed them down. Just point guard stuff that’s really nice for a young player.”

Scalabrine says Rondo’s intelligence made him a great leader early on -- “He’s probably our smartest basketball player. He has like a photographic memory. Once he sees something one time, that’s it. He knows all the plays,” he said -- while Tony Allen says it was team-first attitude.

“He’s a 100 percent team player,” said Allen. “He always tries to get his guys involved first and whenever he feels like he wants to take that turn or when he wants to score, passing, he just picks his poison whenever he wants to let it out.”

Three seasons ago, Rondo’s teammates first recognized a young rookie’s potential. Now they cannot say enough about the player who has become the leader of a veteran team at just 24 years old.

“I think right now, he’s the best player on our team,” Perkins said. “Without Rondo, nothing goes. Pretty much we’ve got to play him the whole game because he just runs the whole team. Without him, we’d be dead.”

Said Scalabrine, “He was special from the first day he was here and he’s gotten better at that every day. He has special qualities that no matter what, you can’t teach. I can’t believe people overlooked that, but they did, so it’s fortunate for us that we have him. But his level of basketball is just different. He’s like a star. He’s not just a role player or a point guard, like most people thought he was.”

For those who thought the point guard from Kentucky would never make an impact because of his jumper, he has been scoring at will during the Eastern Conference semifinals. He is averaging more than 20 points per game and shooting nearly 53 percent from the floor. (He has even knocked down the occasional 3-pointer.) Rondo’s performance on both ends of the court has been so strong it prompted a cheer traditionally chanted for his veteran teammates.

“He’s grown leaps and bounds,” Pierce said. “He’s showing that he’s an All-Star. But the more and more he performs at this level, he’s going to show that he’s going to be a perennial All-Star, which is the next level, and then hopefully maybe an MVP candidate. You heard how they were chanting 'M-V-P,' so if he can sustain that type of play throughout a whole NBA season, you never know.”

Four years after being drafted by the Celtics, the player Rivers once thought had “no chance” has given the Celtics a chance at postseason success.

“I don’t know if I’m surprised. I can say I’m happy more than surprised,” Rivers said. “I knew he’d get there, I didn’t know how long it would take.”

If the Celtics have it their way, it will take less than seven games.