WALTHAM — Much of the talk this preseason has been about the Celtics ‘ flexibility and versatility and coach Doc Rivers  is already experimenting. Rookie Jared Sullinger was in the starting lineup for their final exhibition game in Milan and he played well, scoring 25 points to go with 15 rebounds in their two games.
When the curtain rose on practice on Wednesday, Sullinger was back out there with the starting lineup that also included Rajon Rondo , Jason Terry , Paul Pierce  and Kevin Garnett . So, Doc, how much should we read into that?
“I’m going to try it for a couple of games and I’ll throw Brandon [Bass ] in. I’ll throw Darko [Milicic ] in a couple of times,” Rivers said. “You can read into it whatever you want, but there’s been no decisions made on anything yet.”
This opens up a host of intriguing possibilities. Rivers said he could use Darko at center so Garnett, “doesn’t have a wrestling match with the bigs the entire season. There’s a lot of thoughts. We may go to a transitional starting lineup, have three different starting lineups. We’ve put a lot of thought into it, we’ll just figure it out. ”
That makes sense against a number of Eastern Conference teams including the Pacers (Roy Hibbert ), Sixers (Andrew Bynum ), and Nets (Brook Lopez ), to name three. Sullinger’s emergence may tell a different story, however. He was praised by Rivers, Garnett and Rondo for his on-court intelligence and it goes without saying that rookies don’t receive those kind of kudos.
“He doesn’t think like a rookie. He thinks like a veteran,” Rivers said. “He plays at a great pace. He’s one of our best rebounders. He can pass the ball. He does a lot of things that help our team so we just want to keep moving guys around.”
Or as Rondo put it, “He’s probably the smartest rookie we’ve had since I’ve been here. He’s very intelligent. High basketball IQ and he’s very unselfish. He doesn’t need a play called for him. He’s been getting his points off the dirty work.”
Of course, this could also present a dilemma. Bass has done nothing to lose his starting job and in fact, he helped save their season when he moved from a productive bench role to the starting lineup at midseason. But Bass, along with Terry and to a lesser extent Courtney Lee , have all handled starting and reserve roles throughout their career.
“My job is to play,” Rondo said. “Whether Doc throws an eight grader out there, I have to try to make his job easy and bring the best out of them. Brandon’s handling it very well. He’s mature. It’s not set in stone. He played terrific for us and with that second lineup he rebounded the ball tremendously. He shot the ball extremely well. I think he’s willing to accept his role, whether he starts or comes off the bench. That shows a lot about Jared too. This is the most flexible we’ve had here since I’ve been a Celtic. Bottom line.”
For his part, Rivers doesn’t try to talk guys into accepting their roles. Rather, he expects them to handle whatever job is assigned.
“I don’t tell them that,” he said. “I think they figure it out. I’ve had problems with that with some guys and other guys you don’t. It’s not always going to be roses. What I try to tell them is we’re playing for something as a group and everyone has a role and we need you to buy into that. Some guys who are actually good guys haven’t and some guys who have been not great teammates other places have come in here and done it. I wish I knew the formula, but I don’t. I don’t ask a lot with that. We just do it, and we hope they handle it.”
What’s left, then, is a far more fluid team than we’re used to seeing with the Celtics. Left unsaid is Garnett’s impact on whoever’s out there on the floor with him, and just as importantly, who’s on the court when he’s not in the game.
Simply put, any lineup with Garnett on the court is going to be strong defensively and his presence should help a rookie like Sullinger get acclimated to the defensive demands in the NBA. Additionally, the Celtics were beyond bad last season when Garnett was out of the game, especially in the postseason.
Right now the Celtics have 10 players who can play rotation minutes. (That goes up to 11 when Avery Bradley  returns, which Rivers said was still a long way away). Players like Lee, Terry, Bass, Darko, Jason Collins  and Jeff Green  could form the backbone of a far more dynamic second unit and that’s where Rivers true attention is at these days.
“I’m not worried about our starting lineup,” Rivers said. “I’m far more worried about our second lineup. That’s the lineup that we’re going to keep moving guys around. I’ve said it before, if you can take a starter and put him on the second unit that’s good for the second unit. I don’t know if we’ll do that, but we may.”