WALTHAM — Talk about walking a fine line.

Doc Rivers knows his team – and Kendrick Perkins in particular – needs to do just that to come away with its 18th NBA title when they match up against the Lakers in the next two weeks.

Rivers was told by more than one member of the recently-excused Phoenix Suns that if you plan on carrying through with the directive of Celtics fans everywhere, you better bring your hard hats and be prepared to rebound against the defending NBA champs.

That, of course, means being physical and not backing down. That also means that Kendrick Perkins needs to play with perfectly-controlled fury or risk his seventh technical foul, bringing with it an automatic one-game suspension.

“Our talks [with Perkins] haven’t worked yet, so maybe I should have another one,” Rivers said. “I’m concerned by it, honestly. What I’m concerned by with this is that it’s going to be a physical series. There’s going be guys that get tangled up under the basket, and there are going to be officials who are going to want to clean the game up. Perk may be in that. And the double technical — that’s why I’ve been on the double technical thing for a month now. This double technical thing should not be part of the seven techs, it really shouldn’t be. But it is and it’s a factor. And I wouldn’t be surprised if it’s a factor in this series.”

Perkins, Glen Davis, Kevin Garnett, Shelden Williams and Rasheed Wallace – if healthy – will be called upon to contain Pau Gasol, Andrew Bynum, Lamar Odom and Didier Ilunga-Mbenga.

“We’re just going to be us,” Rivers said following Monday’s practice. “I don’t know if that’s with any particular person. We’re going to be us and if that’s physical, that’s what we’re going to be.”