C’s get back to business

Doc Rivers doesn’t have to get too creative while searching for the right words to motivate the Celtics this season. He just needs to point overhead.

The Celtics reunited as a whole yesterday at the team’s practice facility in Waltham for 2008 media day, and Rivers’ message was concise. Notice the pattern with the championship banners? The great teams went back-to-back.

“You ask yourself, ‘What’s the next challenge?’” said Paul Pierce. “Of all the great players and great teams that have been here as Celtics, they did it more than once. That’s the challenge now. I thought about it all throughout the summer.”

The drive to excel through each minute of every game and every practice for a second straight season could dictate the fate of this year’s team, but Pierce and company chalked it up to business as usual.

“I don’t know how to do it any other way,” Ray Allen said. “When we start, there’s a certain level of commitment that we have to give, and none of us want any less.”

One surprise yesterday was the arrival of Sam Cassell, who will turn 39 in November. Cassell is the 16th player under contract, which means Darius Miles’ chances to make the team took a serious hit.

And the first obstacle for the Celtics will be the health of Kendrick Perkins, who is still recovering from shoulder surgery and won’t be ready to participate in contact drills for at least two more weeks.

“I’m expecting to play in the third preseason game,” Perkins said. “I’ll just get in the best shape I possibly can get in, keep [lifting] weights and go from there.”