Doc Rivers has a simple rule, but it’s the basis for everything that makes the Celtics tick. It doesn’t involve an offensive set or a defensive scheme. It’s not about matchups, rotations or help-side pick and roll defense.
The rule is this: respect each other.
With that simple principle in place the Celtics are free to rip each other unmercilessly and dunk on each other’s heads when they’re not looking. It takes a thick skin to survive with the Celtics, but it also takes the ability to laugh at oneself and the wisdom to not take the joke too far.
“The only rule I have is called the respect rule,” Rivers said. “If anything is getting to where it’s disrespecting someone to where it’s a problem, then it’s a problem. They enjoy each other. I’m sure they’ll cross the line at some point, but that’s fine.”
A lot has been made about Nate Robinson’s antics during camp along with his regular foil, Shaquille O’Neal. There’s video, posted by Robinson of course, of him dunking on Shaq and running in his oversized shoes. There’s photos of Robinson messing with the big fella while he’s sleeping on the team bus.
The Nate and Shaq show been a welcome blast of sunshine to what had become a rather grim team the last few seasons and it fits perfectly into Rivers’ guideline. It also fits within another of the coach’s parameters, which is to understand the difference between work and play.  
“They’re serious in practice, after that they’re grown men,” Rivers said. “I don’t care how they act. They want to have fun or embarrass themselves I really don’t care.”
That’s an underrated aspect of Rivers’ coaching genius and one of the reasons why veterans want to play for him. He allows players the freedom to be themselves and express themselves the way they want, so long as it doesn’t interfere with work.
“We’re a loose, focused, hard-working group,” is how Paul Pierce put it. “A lot of people say that we went down [to Newport] to have fun and goof around, but that’s not necessarily the case. There’s a time and a place for everything. I think we’re having a good balance between the two.”
Jermaine O’Neal has only been with the Celtics for a little more than a week, but he’s already marveling about how things are done here. There was movie night in Newport and team dinners on other evenings. Back in Boston, the team gathered for a duck boat ride and then ate brunch together on their off day.
All of that: the dinners, the team events, and the clowning make up the foundation of what we like to call chemistry. But this is something a little more than that and when O’Neal sees it, he recognizes what it isn’t as much as what it is.
“That’s a real situation in pro sports that people don’t talk about,” he said. “In Indiana we had some really good teams, but we couldn’t get over the hump because that togetherness wasn’t quite there.” 
Chemistry is at once one of the most important elements of a championship team and also one of the most fundamentally overrated because it doesn’t add any points on the scoreboard and it doesn’t help you make a shot.
There’s an old professional sports maxim that goes something like this: “Give me a team on a winning streak and I’ll show you good chemistry. Give me the same team on a losing streak and I’ll show you a team that can’t stand each other.”
It’s no surprise that successful teams point to their camaraderie as a key ingredient while losing teams simply point the finger, but what the Celtics are going for is just a little bit different.
They’re not just trying to take the good things from the court and transfer them to the locker room, they’re trying to take the good things from the locker room and transfer them back on to the court.
That’s not just saying the right things about shots and minutes. That’s trying to make it so that none of it feels like a sacrifice.
“When you’re social and you’re actually trying to get to know the next guy, it makes things on the court a little easier,” Kevin Garnett said earlier in camp. “I think everyone’s embracing it and opening up instead of shutting it off and doing their own thing. I think we have a locker room that’s very open.” 
Jermaine O’Neal thought about that notion for a minute and then nodded back to the floor.
“If you can depend on someone away from basketball, this is easy,” he said. “It’s easy money when you get on the court. One of the things we talked about is staying together. People look at what Shaq and Nate are doing and think there’s a lot of joking around.
“One thing that has to be said, this team jokes around a lot when we’re in the locker room, [but] when we step on the court it’s all business. It’s never personal. We make that clear.” 
This Celtics season is one huge experiment with roots in not just chemistry, but biology (age) and psychology (motivation), as well. The semester has barely begun, but the orientation seems to have gone remarkably well.