Going into this week, it looked fairly clear that Jermaine O'Neal was the heavy favorite to land the Celtics' starting center position vacated by the injured Kendrick Perkins. At six years younger and a good deal more athletic than the other O'Neal in the building, J.O. seemed like the right guy for the job.

But the other O'Neal has emerged this week looking surprisingly motivated. Based on his workouts this week, it looks like he's got a shot at cracking into Doc Rivers' starting five — if he wants it.

"I don't know if he does or not, but I know he's playing his butt off," the Celtics' coach said of Shaquille O'Neal. "Just watching what he's doing, he doesn't care. He just wants to play and help the team. You can see that he really wants to prove he can play still, number one. And I think he just wants to win, and you can see that. And I think that's why it's been easy so far — he doesn't care what unit he's with. That makes a big difference. It helps my job."

When the C's got underway in Newport, R.I. on Tuesday morning, they had Jermaine O'Neal decked out in a green practice jersey along with the rest of the Celtics' starting five. Shaquille, dressed in white, worked with the second unit. The two scrimmaged with their respective five-man groups for most of the first three days of camp, and both seemed happy in their roles.

But Shaq kept working — hard enough that by week's end, the coach became curious enough to try him out with the C's starters.

"Shaq was phenomenal," Rivers said. "He had a great camp. He's in very good shape, and he had a very impressive camp.

"Shaq might have been the biggest surprise. He's fit in extremely well."

Each of Rivers' "O'Neal brothers" presents a different element to the starting five. Jermaine brings youth, energy, quickness, and a defense-first attitude. Shaq brings size, strength, experience, and a whole new dimension to the Celtics' offense.

Jermaine may still be the favorite to land the starting job, but Shaq is proving that he also brings something to the table.

"They're progressing fine," Kevin Garnett said of the two centers. "J.O. is good because of his versatility. He can do different things. We play a lot of different games when he's in there. He's very talkative, we communicate really well.

"And Shaq, he's very simple. A lot of things are simplified when it comes to his presence. When he's down there, it makes a lot of things easy."

A lot of things have been easy for the Celtics in camp. The biggest challenge of all, though, is deciding on a center. That decision may have gotten even tougher this week.

NESN.com will showcase one Moment of Shaq every day until the Celtics open the season against the Heat on Oct. 26 at the TD Garden.

Friday, Oct. 1: Shaq gets pranked again.