“I’m just trying to find my niche here. It’s been tough, but it’s been coming along,” said former Georgetown star Jeff Green of adjusting to his role with the Boston Celtics, who acquired the forward from Oklahoma City Thunder at the trade deadline. (Mike Ehrmann/Getty Images)

It took him about a week to get over the sadness and disbelief after being traded by the only franchise he had played for in his first 31 / 2 seasons in the NBA. Jeff Green didn’t have much time to wallow after the Oklahoma City Thunder dealt him to the Boston Celtics at the trade deadline, because the task put before him — to back up two potential Hall of Famers in Paul Pierce and Ray Allen and help the league’s most storied organization claim an 18th NBA championship — was daunting enough.

In the nearly two months since Green donned green, the former Georgetown star has had to adjust to being a backup after being a starter, to playing small forward after being used primarily at power forward, and to being a defensive specialist after being an occasional offensive threat.

“Those are big adjustments in a short period of time, on a team that’s trying to win a title,” Celtics Coach Doc Rivers said on Friday. “We’re asking a lot. We knew that. And he’s doing his best.”

Green has overcome his initial confusion with the changes, and no longer feels overwhelmed, but he is still trying to find his way.

“It’s been a whirlwind. Especially the beginning, coming to Boston, going to a new team, first time getting traded, going to a high-profile team, a lot of expectations. It was tough,” Green said as the Celtics prepared to host the Miami Heat in Game 3 of their Eastern Conference semifinal series on Saturday at TD Garden. “When you’re in a situation like I was in, you don’t think stuff like that can happen. You look past it, like, ‘That could never be me, I could never be in that position.’ And when it happened, I was kind of shocked. It was tough, the first couple of days, to get over it. But eventually, I did.”

When his season began in Oklahoma City, Green said the team had aspirations to make significant progress after losing a tough, six-game, first-round series against the Los Angeles Lakers. But when he arrived in Boston — where the Celtics have won a championship and reached the NBA Finals twice in the past three seasons — he knew right away that the goals are “much higher. It’s different, coming from a situation where the goal is to make it out to the playoffs, get out of the first round. Here it’s a championship or it’s a fail.”

The Celtics trail 2-0 in the best-of-seven series, and if they fail to defeat the Heat, or at least return to the NBA Finals, President of Basketball Operations Danny Ainge’s decision to swap the hugely popular Kendrick Perkins to get Green will receive more negative scrutiny than it already has. Green was easily the most skilled player acquired in the deal, but Perkins brought a physical presence, a constant scowl and an edge that made him well-liked within the locker room and a fan favorite.

“I look at it like it wasn’t no pressure,” Green said. “I was dealt for a player who was yes, a centerpiece of this team, but we’re not the same position. So it’s not a lot of pressure for me to fill in what he did for this team. My thing was to come in and do what I could do. Not try to replace what Perk did.”

Ainge brought in the 6-foot-9 Green with the hope that he could give Rivers some versatile lineups and spare wearing down Pierce by forcing him to expend so much energy defending elite perimeter players. Green found himself defending Amare Stoudemire, Carmelo Anthony and even Chauncey Billups in the Celtics’ first-round sweep of the New York Knicks. He has been matched up primarily against Heat all-star LeBron James and admitted, “there’s no one guy in this league who has the keys to success of guarding LeBron.

“It’s a great opportunity for myself, for a lot of people to see what I can do,” Green said of playing for a higher-profile team. “It’s been tough at times, because you get used to playing so many minutes and you have to develop a certain mentality coming off the bench. It’s very difficult. I’m just trying to find my niche here. It’s been tough, but it’s been coming along.”

Green rejected a contract extension from the Thunder last summer, which likely prompted his trade, and will be a restricted free agent this offseason. His family and friends were excited that the trade with Boston brought him closer to home, but Green chuckled when asked if he could see himself eventually playing for his hometown Wizards.

“I could see myself playing anywhere,” said Green, who won a state title at Northwestern in Hyattsville. “I love playing basketball. D.C. is a great city, a great environment. They have a great team, new ownership, heading in the right direction and if the chance comes to be there, I’d love to be home. But right now I’m here in Boston, trying to make the best of the opportunities I have here.

“Everybody wants to win a championship and for me to be in the position I’m in, I have a great chance, with the guys who have been here and already won one, they know what it takes,” Green said. “I’m just riding with them and trying to do the best I can to help them get to that situation. It’s been fun, I’m enjoying the ride.”