The theory presented to him Monday is one that a growing faction of Celtics fans favor. It has been out there for a while, mind you, but it has picked up steam as the Celtics have reeled off four straight wins without guard Rajon Rondo, who is out for the season because of a knee injury.

The core concept is that the Celtics are, somehow, better off without Rondo. They are 18-20 when Rondo plays, 6-3 when he doesn’t.

“I don’t think so,” Pierce said after reading to a large group of students as part of the team’s Read to Achieve program. “We won a championship with Rondo. We’ve had great seasons with Rondo being healthy. I really don’t buy into that notion. Like I told you, we’re just coming together. We’re using the injuries as motivation — and we’re actually playing for Rondo.”

There are numbers worth considering.

In the Celtics’ first 43 games, in which Rondo played 38, they:

■  Scored about 95 points a game and gave up about 96.

■  Shot about 46 percent from the floor, while opponents shot about 45 percent.

■  Averaged about 23 assists a game.

■  Posted a 20-23 record.

And in the Celtics’ four games since Rondo was injured, they:

■  Scored about 101 points a game and gave up about 92.

■  Shot about 48 percent from the floor, while opponents have shot about 42 percent.

■  Averaged about 25 assists a game.

■  Posted a 4-0 record.

Granted, that’s a small sample size: four games vs. 43. And, yes, the differences in those numbers do not rest solely on Rondo’s presence or lack thereof. His absence was, in fact, strongly felt late Sunday, when the Clippers nearly came back from a 19-point deficit to steal a win.

Still, the statistics don’t lie: The Celtics are playing better basketball of late.

Pierce doesn’t believe they’re playing better because Rondo is out of the lineup, though.

Instead, Pierce points to “togetherness” as the reason they’re clicking so well as a unit without their All-Star floor general — and also without emerging rookie forward Jared Sullinger, who is lost for the season because of back surgery.

“We understand the situation with the injuries,” Pierce said, “but I think that’s something that’s brought us together even closer.

“A lot of people have pretty much written us off, which is fine, but the only people that haven’t written us off is us, in that locker room. We continue to keep a strong bond [in] there with what we’ve got.”

Guard Courtney Lee, who has stepped into Rondo’s starting role, was also presented with the question regarding whether Boston was, in fact, a better basketball team minus Rondo.

“I wouldn’t say that at all,” Lee said after the Celtics beat the Clippers, 106-104, Sunday at the Garden. “Rondo is an All-Star. Anytime you can add an All-Star to your team, your team is going to be better. We definitely miss Rondo. We don’t look at it as, ‘We’re better off without Rondo.’ I think we came together and we’re playing hard for Rondo — and Sullinger.”

There is no doubt that the Celtics have banded together in the wake of their fallen comrades. And just as Pierce believes that everyone has written them off, other Celtics believe so too, using that idea — however real or manufactured it may be — as fuel.

“A lot of people say that we don’t have a chance to go to the playoffs, we can’t do this, we can’t do that,” guard Avery Bradley said Sunday. “We know that we have each other, and we’re going to go out there and fight for each other no matter what, every single night.”

So, have the Celtics simply united as one? Is that the sole reason they’re winning? Hardly.

In reality, the Celtics are sharing the ball at an increased rate as compared with before, when Rondo dominated the ball-handling duties, as was his specialty.

It’s a marked difference and defenses, which were used to keying on Rondo, haven’t adjusted.

“It’s important for everybody to get shots, but it’s more important to have everybody involved,” Kevin Garnett said Sunday. “No one wants to be on the floor and not touch the ball, but I think that’s what made us successful of late, involving everybody, one through however many [there] is of us.”

Doc Rivers could only agree.

“Listen: It’s not a hard way to play,” the Celtics coach said Sunday. “Shoot the ball when you’re open or pass it. Really. That’s all we’re telling guys to do. If you’re open and it’s your shot, shoot it, no hesitation.”

.   .   .