Former Georgetown star Jeff Green, who is averaging 19 points in three playoff games for Boston less than 16 months after heart surgery, passes the ball against New York on Friday. He had 21 points and nine rebounds in the 90-76 loss. (CJ Gunther/EPA)

When Jeff Green’s name is announced with the Boston Celtics’ starters at TD Garden, he shoots from his seat and slaps five through two lines of teammates until he reaches Jason Terry. At that point, Green presses his fists against his sternum and pulls them apart, pantomiming tearing open his chest.

Terry, who sits in the adjacent locker room stall, has given Green the nickname “Iron Man,” after the comic-book superhero with a hole in his chest and shrapnel near his heart. Green does the same chest-ripping gesture after an emphatic dunk or any other highlight-worthy play, reminders that while Green might not save lives and destroy bad guys like the make-believe Tony Stark, he remains on a spectacular journey nearly 16 months after surgery to fix an aortic aneurysm.

“You know, I’m blessed,” said Green, 26. “Last year, I missed the whole season, dealing with surgery on my heart. That’s not something you hear too often in this league and it’s not something a guy my age and only a couple of years in the league wanted to hear. But to be in position to play in every game this year, in addition to these playoffs, and the confidence that I’ve played the game has been better than ever. I’m still a work in progress, but I’m in a great position.”

Green, the former standout at Georgetown University and Hyattsville’s Northwestern High, has been the Celtics’ leading scorer in their playoff series against the New York Knicks, averaging 19 points through the first three games. New York has dominated the Celtics and has an opportunity to complete a sweep on Sunday at 1 p.m., but Green isn’t willing to surrender anything. “They haven’t won it yet. As long as we’re still playing, we have a chance,” Green said, though no NBA team has ever come back from a 3-0 deficit to win a playoff series.

Green has been counted out before. Each whirling drive and turnaround jumper is a testament to how far he has come since undergoing five hours of surgery on Jan. 9, 2012. He remembers having to press a pillow against his chest to limit the pain whenever he coughed or sneezed, and the feeling of accomplishment when he was finally able to take 10 steps without gasping for air.

Green readily admits that he hasn’t fully recovered and that he continues to grapple with his conditioning. While he must pay closer attention to his body, he is also proud to flaunt it. Though he wears a customized, padded tank top beneath his uniform to protect himself during games, Green will walk around shirtless after practice, exposing the nearly foot-long scar down the middle of his chest.

“It’s me. The new me,” Green said proudly. “Something that shows what I’ve been through. It shows my character. God puts you in positions to succeed and he humbles you. And that scar humbled me and made me appreciate life a lot more, because it was almost taken from me. And the game I love was almost taken from me.”

Green arrived in Boston in early December 2011 to take a routine physical and sign a one-year qualifying offer worth $9 million to return to the team that acquired him for fan favorite Kendrick Perkins 10 months before. He barely had time to celebrate his new deal before he learned that he had failed his stress test and that a rapidly expanding aortic root and a leaking aortic valve required surgery.

“It was a big shock to the system,” said Green’s best friend, Willie Jennings. “You don’t get a lot from Jeff, as far as emotions. But when he first found out, it was tough. He actually shed some tears. It was the first time I actually seen him cry.”

Indiana Pacers center Roy Hibbert, Green’s teammate for three seasons at Georgetown, was stunned to hear the news as well because he had been training with Green throughout that offseason, which was extended by the NBA lockout. They ran on the treadmill, played pickup games with other players, including Detroit’s Greg Monroe, and he never had a concern that anything was wrong.

“He was killing in those workouts,” Hibbert said of Green. “I was sad ’cause I had just seen him four days before running up and down the court, dunking and everything. It was God telling him something ’cause if the lockout didn’t end, something bad could have really happened to him.”

Green said the “end of the lockout saved my life,” a belief that was affirmed by Lars Svensson, a cardiac surgeon at Cleveland Clinic in Ohio who explained to Green that the aneurysm was rapidly growing and needed immediate attention.

“It was an incredible setback for a young player entering his peak performance years and he was very accepting,” Svensson said in a telephone interview. “I tried to reassure him as much as possible that you have to have a structural problem fixed and you’ll be able to play again once you have it fixed.”

The night before his heart surgery, Green stayed up until 2 a.m. playing the video game Call of Duty with Jennings, who helped keep the mood light with some jokes and trash talking. Jennings said Green remained calm and “played it cool” in the hours before the procedure.

“There is always fear, but I put my faith in God and I put it in His hands. Nothing I could do about it,” Green said.

The Celtics withdrew Green’s qualifying offer before the surgery but Boston Coach Doc Rivers and Danny Ainge, the president of basketball operations, continued to let him be around the team even though he wasn’t under contract. After he gained enough strength to begin his rehabilitation in Boston in March 2012, Green would hang out in the locker room and watch games from the bench.

“It was tough. For a while, I had to stop watching,” Green said. “I mean, it was good to be around the guys, the brotherhood, the camaraderie of everybody made me feel like I was part of the team, but not really. I felt like I needed that at that point in my recovery stage.”

Green was cleared to begin basketball-related activities in June but waited a month before he started playing pickup games at Georgetown. His confidence grew after absorbing every hit and the Celtics eventually showed their faith by signing Green to a four-year, $36-million contract.

“I think people mislabel him sometimes because he’s so quiet and you get that mixed up with not having intensity or whatever,” Rivers said of Green. “He’s a tough kid, obviously. Basketball after a heart surgery and doing it well. And now his next step is to become great and he has the ability to do that. He just knows that there is work to do still. And what I love about him is, he’s willing to do it.”

The 6-foot-9, 230-pound Green has repaid the Celtics’ confidence with a solid campaign in which he played a team-high 81 games, averaging 12.8 points and 3.9 rebounds per game.

Green’s most inspirational moment came when he scored 21 points, including the game-winning layup as time expired, in a 93-92 win on March 27 in Cleveland with Svensson in attendance. On his way off the court, Green tracked down Svensson and gave him a hug.

“That was just fantastic,” Svensson said. “Jeff, to his credit, he had the mental stamina and endurance to get back to super athlete performance again. He’s got incredible mental ability.”

“It was amazing to do it, in the place that I had the surgery in front of the doctor who basically saved my life,” Green said. “It was a surreal moment. To be in that position to do that in front of him and he really enjoyed it. . . . With the level I want to be at — an all-star and one of the top players in this league — some of the things that I’ve been through this year, as far as being a leader on the team, it matured me a lot. I think I needed that to be the kind of player that I want to be. And I think the sky’s the limit from here.”