The decision was made before the game, and it was the last major one the Celtics would have to make before the start of the playoffs. With Jermaine O’Neal and Nenad Krstic both available, Doc Rivers elected to start O’Neal and bring Krstic off the bench.

“JO’s playing well,” Rivers said. “That’s probably where Krstic will [be] during the playoffs, so put him there now and let him get used to that and that role.”

With O’Neal taking his place alongside Rajon Rondo, Ray Allen, Paul Pierce and Kevin Garnett, the Celtics have that defensive presence to start the games. With Krstic coming off the bench, he can focus on doing what he does best: make jump shots and provide another big body to play with Glen Davis and Jeff Green.

“It was great having another big who can spread the floor,” Green said. “I’ve been with Nenad for a couple of years now and I know what he can do so it was a lot easier for myself, just having a big along with Baby.”

There were a lot of things to like about the Celtics' 99-82 win over the 76ers Tuesday night (click here for a full recap), but the lineup change was the most important consideration as they head into the last week of the regular season. Together, the Celtics centers put up 17 points and nine rebounds in 30 minutes of action (Davis played the other minutes). That’s a good night’s work for any center rotation, especially one in which the position is the fifth option.

“JO was terrific,” Rivers said. “He was aggressive, he was attacking, his defense was phenomenal. I mean, he’s just been really good since he’s been back. He just buys in. We rarely go to him but he gets the ball in the right places because he’s in the right spots. I liked Krstic early on being aggressive and that’s what we’re trying to get him back to doing.”

This isn’t about O’Neal and the starters as much as it is Krstic and the second unit. The reality is that everyone looks better playing with the four All-Stars. But the reserve corps has been in a state of flux all season and this has a chance to rapidly become a strength.

Green has shown to be a much more effective player with two big men, and both of the Oklahoma City transplants have shown a tendency to defer when playing with the big four. Of course, one of them will have to be on the floor with them, and Rivers used various combinations involving Rondo, Allen and Pierce. That will still sort itself out depending on the matchup or foul trouble, but finally a second unit has emerged and it’s certainly more talented than any they used even before the trades.

After an offensive-minded first half, the starters put together a nice defensive run to open the second and built a 10-point lead. Ten quickly became four, but the reserve unit pushed it back to double digits by the end of the quarter and then expanded the lead in the fourth.

“That was huge for us,” Rivers said. “And listen, we’re getting healthier so our bench is starting to resemble a bench. That’s good.”

Also good was the play of O’Neal, who scored nine points with most of it coming on easy dunks. Scoring is not O’Neal’s focus and he noted that while his offensive rhythm is making progress, it’s really his mobility that’s the important factor.

“Covering ground, covering the pick and roll felt really good,” O’Neal said. “I’m being able to make multiple moves, being able to show, get back to the basket and contest a shot. Those are the things I’m really trying to concentrate on.”

Having Shaquille O’Neal would tie everything together in a neat bow, because no one has played better with the starters than Shaq. But the Celtics really don’t know whether that’s a realistic possibility. He may play again before the end of the season and he just as easily may not. They have to prepare one way or another and they took a very important step Tuesday night.

Here are three more points:

THE COMFORT FACTOR

It can’t be easy coming to a new team, especially one with championship aspirations, not to mention three Hall of Famers and a fourth All-Star who is just beginning to write his legacy. At times, both Green and Krstic have struggled with the burden. Rivers has felt that Green has deferred too much, while Krstic has simply let his brain get in the way of his body.

“It’s very tough,” Green said. “When you got guys like Ray on one wing, Paul on one wing, Kevin on the block. You want to share the ball and when you got great players you know they can knock down shots so it’s fun also. You also have to be aware of what you can do and when you can be aggressive.”

As for Krstic, he said, “I realize thinking about making the right play is not going to help. Just play basketball. If I make mistakes coach is going to yell at me for five seconds and then, next play.”

There is also an adjustment period for playing for a demanding coach like Rivers. He has aired out Krstic during games and Green said Rivers has been on him from the first practice.

“He’s always on me,” Green said. “I learned that the first day I got here. The first practice, he was on me. He told me he sees a bright future in myself and he was going to push me to be the best player I can be. He just wants me to go out there and play my game.”

Just playing their game has been the hard part, but when they do it has resulted in good things.

RAJON RONDO TURNED IT ON

In the first quarter, Sixers point guard Jrue Holiday went off for 11 points. He didn’t score the rest of the game. Rondo, meanwhile, put up 16 points and 14 assists.

“He probably has the most responsibility on both ends of the floor,” Garnett said. “Tonight was evident of that. When he decided to guard and he decided to slow Holiday down, their whole offense slowed down also.”

It’s also been evident for the past month that the veteran stars have been placing themselves at times. None has been more obvious than Rondo, but over the last week he has come out more aggressive and the results have been equally apparent.

This is understandable. It’s also been frustrating. But in the time-honored words of the local football coach, “It is what it is.”

“He was just aggressive and attacking and shooting,” Rivers said. “You can see he’s getting himself ready, you can just feel that. I don’t know if he plays with great focus all game or if any of our guys do. But you can see what they’re all doing. They’re in some way sharpening their tools. In spurts. They know where they’re that.”

As he often does, Rondo said he was fine. “Yeah, I’m OK,” he said. “Trying to keep the turnovers down.”

That’s about as deep as he usually comes to breaking down his own game, but he took it a step further.

“I got to make the simple pass but at the same time I’m a risk taker,” he said. “I try to make plays for my teammates. Whether it’s a behind the back pass or a regular bounce pass, any way I’m able to do that that’s the best way is what I do.”

When Rondo’s at his best, he channels that creative risk-taking and becomes one of the more brilliant players in the sport. It’s not always as simple as deciding to do it, but he has the ability to make it seem that way and as Rivers said, he knows where he’s at.

TAKE A MOMENT TO APPRECIATE KEVIN GARNETT’S DEFENSE

Kevin Garnett won’t win the Defensive Player of the Year award. That seems to have Dwight Howard’s name permanently engraved on it for the foreseeable future, and for good reason. But as a team defender, Garnett has no equal.

“If it was called the Defensive Most Valuable Player, I think Kevin Garnett should win it,” Rivers said in a quiet moment after practice on Monday.

He played 24 minutes and scored just 14 points to go with three rebounds, but as usual, numbers rarely tell the story. Garnett took Spencer Hawes completely out of the game. He locked down Thaddeus Young. He went tote-to-toe with Elton Brand. When Holiday was killing them with pick and rolls he showed hard and knocked him off line.

Most remarkable, he’s been doing it all season long. Garnett is happy to fly below the radar. As long as things are flowing, he’s content to take a back seat when praise is being thrown around. He doesn’t need the adulation, but he should get some for the work he’s done this season.