WALTHAM, Mass. -- Jermaine O'Neal readily admits he's not the offensive player he used to be. His body grinded down from 14 NBA seasons, he can't jump as high as he used to nor move as quickly in the post as he once did.
His offensive game has drifted further and further away from the basket and his scoring average has dipped more than 10 points per game since the 2004-05 season, when he averaged 24.3 points per game for the Indiana Pacers (last season he chipped in 13.6 points per game in Miami).
He knows the casual NBA fan will continue to judge him based on his offensive numbers, which will predictably dip again this season with the Boston Celtics, especially in a reserve role. But to him it doesn't matter.
He's come to grips with the idea of sacrifice, especially if it leads to the prize he covets most: an NBA title.
In fact, it was on his 32nd birthday that he had a realization that -- after roughly 1,000 career NBA games (preseason, regular season and playoffs combined) -- defense will be what defines him in Boston.
"It's not about [scoring] right now," O'Neal said Friday after returning to practice for the first time since tearing cartilage in his left wrist a week ago in Toronto. "The first time it ever donned on me was in New York [this preseason]. I had a guy on me that I felt like I could take, but I didn't see one post-up against him all night.
"That's what me and [Shaquille O'Neal] have talked a lot about: Do what the team needs us to do in order to be successful. Ray [Allen] talked about it with me [Friday] morning, saying how we don't care who plays, we just support each other and we root for each other."
It's been what Celtics coach Doc Rivers dubbed a "disappointing" preseason for Jermaine O'Neal. He missed part of training camp with a sore left hamstring, then tweaked his back. After injuring the wrist in Toronto, he took a full week off to heal.
O'Neal appeared in only four exhibition games, averaging three points, five rebounds and two blocks in 15.3 minutes per contest. The missed time leaves his role hazy as Tuesday's season opener approaches, but O'Neal deemed himself ready to contribute in whatever role emerges.
That role is likely to focus heavily on defense, which is fine by him.
Amidst the backdrop of offensive depreciation, his inspired play at the other end of the court is being thrust into a larger spotlight, which he finds rather amusing.
"It's funny to hear about my shot-blocking abilities now," he said. "I already own the all-time shot-blocking record in Indiana. I already own the state of South Carolina's high school shot-blocking record. I've always played defense. Do the research: As much as I scored in Indiana, I've always been one of the top charge-takers in the league. I've always concentrated on defense."
Before Wednesday's exhibition finale against the New Jersey Nets, Rivers admitted he didn't know what O'Neal would be able to contribute by the start of the regular season. He remained cautiously optimistic Friday, noting it was just one of four practices leading up to opening night.
O'Neal planned a post-practice jog on the treadmill to help build the cardio he's lacking. He stayed late after a 2 1/2-hour session to work on offensive sets, still learning the intricacies of Boston's playbook.
And every time the conversation shifted back to his offensive struggles, O'Neal remained steadfast about being a defense-first player.
"I know what my role is and that's what I'm going to do," he said. "I know people will gauge me on how I shoot the ball or if I'm scoring points. That's fine. That's not the job given to me, though. I know Paul [Pierce] is the first option, then Ray and Kevin [Garnett] and [Rajon] Rondo and everybody else. I knew that when I came here. & It's rebounding, blocking shots, controlling the defensive part of the game; being a presence on the weak side. That's my job."
His job 10 seasons ago consisted of scoring big points and being the focal point of the offense, something he never relished, especially after being shipped to Toronto and Miami as his production dipped.
His all-around game helped him net six All-Star appearances, but though he's not the same player any more he remains just as prideful.
"I can't be the Jermaine O'Neal from 10 years ago," he said. "I can't jump as high as I used to, but I'm a lot smarter. I can tell you this: I'm one of the best in the league at covering ground. I will block shots on the weak side. I will rebound. If they are judging me on offensive-scoring abilities, it's not going to be that way.
"I knew that when I signed here; nor would I want it to be that way. I didn't come here to score. I came here to be involved in something special. & I've never even been to [an NBA] Finals game. I've been in the Eastern Conference finals, but after you endure everything you do, you want to be involved in the [title games]. That's what I'm about.
"I know there will be people out there that say, 'Oh, four points this game.' That's fine. But if my team wins, they can say whatever they want to say."
Chris Forsberg is the Celtics reporter for ESPNBoston.com. Follow him on Twitter.