WALTHAM, Mass. -- If they didn't know what he had endured over the past nine months, Jeff Green would have been driving his teammates crazy on Saturday.
The first day of training camp is rarely a joyful event. Boston Celtics coach Doc Rivers ran his team hard through a three-hour session that, even for the best conditioned players, surely left their lungs burning and muscles aching. It's an unceremonious welcome back to the grind of NBA basketball.
And yet there was Green, with an unshakable grin, chatting up anyone who would listen and even those that wouldn't.
"I was happy to be back on the floor," said Green. "People don't make a big deal out of practice, but I was glad to have a practice under my belt and get going. ... I was trying not to smile too much during practice. I had to keep a straight face. I mean, it's hard.
"I let some emotions go, telling all the players I'm happy to be back, just encouraging them. Just talking a lot for no reason, because I was just glad to be back on the floor."
That's a stark contrast to last December, when a stoic Green stood glued to the sideline as the Celtics opened camp after the lockout lifted. Something in his physical had raised red flags and the team couldn't let him on the floor until they ran more tests.
Those tests uncovered an aortic aneurysm which required surgery and forced Green to sit out the entire 2011-12 season. What's more, he endured a grueling post-surgery rehab to rebuild his stamina and conditioning.
Green hasn't played an NBA game since May 11, 2011, when the Miami Heat bounced Boston from the second round of the Eastern Conference playoffs. He was left with a bad taste in his mouth, feeling like he didn't put his best foot forward during an abbreviated stint with the Celtics after being acquired from the Oklahoma City Thunder at the trade deadline.
So being back out on the floor Saturday for an honest-to-goodness, NBA-sanctioned workout meant a little something extra to Green.
Green admitted even he was confused last year when doctors wouldn't let him on the floor at the start of camp. Even he didn't know the full extent of his condition until word started to spread that it was a heart ailment.
And while the questions about his health and recovery have been relentless -- and he understands why -- Green has stressed that it's all behind him now.
"I've gone through the tough times and I beat it, and now I'm in great condition," he said. "My game is getting right, and I'm just happy to play basketball."
Celtics coach Doc Rivers hammered it home even stronger on Saturday: "Jeff is just as healthy as everybody else. He has no restrictions or anything like that."
So how did he look?
"Jeff looked great," said Rivers. "Actually, he had one of the better practices and I thought his conditioning was phenomenal, so I thought that was great."
Green, drafted by Boston in 2007 before being flipped to Seattle in exchange for Ray Allen, is still only 26 years old. Pierce keeps reminding him that he has only four NBA seasons under his belt, so Pierce said he's "still got the young legs."
Boston's captain is hoping those young legs can carry some of the burden at the swingman spot this season, easing the load on the soon-to-be 35-year-old Pierce.
"You know, he's a guy that makes our lineup so versatile, because he can switch from the 3 to the 4 for a small lineup," said Pierce. "Or he can make us a big lineup with him at the 3 and me at the 2, and it can cause matchup problems. He's going to be a big key for us."
The lingering question is whether the Celtics can get more out of Green than what he's shown in his career thus far. The numbers show that his teams have thrived when he's off the floor as opposed to on it, and he's never truly taken advantage of his blend of size and athleticism.
Green acknowledges he wants to be a better rebounder this season and he wants to be more aggressive at both ends. He wants to use his size to overpower undersized 3s and lean on his speed to outrun bigger 4s. Rivers has put the pressure on himself to find the right fit for Green.
Garnett, for one, thinks there's another level for Green to discover.
"I don't think we've seen the best of Jeff," said Garnett. "I think J-Green -- he has a lot of skill, man. I think, at times, like all of us, we think a lot. He's no different from that. But you see the skill level and you see that confidence coming and it's a process. But, you're kind of marveled at how good he is. So, I don't think we've tapped into that resource yet."
The Celtics believe that, had they had a healthy Green on their bench last season, they would have gotten past the Heat in the Eastern Conference finals and had a chance to play for another title.
Boston bolstered its bench this season by not only bringing back Green, but adding Jason Terry, Courtney Lee, and Darko Milicic. The Celtics brought back Chris Wilcox, who also endured a heart scare last season, missing the last three months of the season with an enlarged aorta.
Green and Wilcox share a special bond. And both were like little kids out on the floor on Saturday (Green joked that he was hogging time at the 4 and Wilcox booted him from the lineup). Pierce smiled when he noted, "You could tell they're anxious; they're excited just to be back out here on the court."
Those smiles will fade soon. They'll endure the grind of camp like everyone else and won't be nearly as chatty on the court. But that's fine by Green. That's all he's wanted to do for the past nine months.