by Jeff Zillgitt, USA TODAY Sports

BROOKLYN — Kevin Garnett sat in a locker room chair last week at the Brooklyn Nets’ Barclays Center and delivered an impassioned defense of Boston Celtics basketball.

“We’re trying to establish something here. You don’t establish that by going through the motions,” he said.. “We’ve never been a go-through the motions team, and I don’t think we’re going to start. I didn’t come back (for an 18th season) to go through the motions. I don’t think the guys who signed came here to go through the motions.

“We are a team that works and works hard. When we’re off, we play hard and we associate with each other. When we touch the floor, it’s all business. … We have a culture here that we adopt. When you put this jersey on, it comes with responsibility, whether it’s preseason, (messin’) around, chillin’, playing 21, whatever it is. It comes with responsibility. We don’t take that lightly around here.”

That is not the sound of a man ready to retire from the NBA. And he makes the case the Celtics are not ready to stop contending for a title, with a new look to this legendary franchise.

Eleven players are gone from last season’s roster. Among the additions are shooting guards Jason Terry and Leandro Barbosa, two-way wing Courtney Lee, versatile and explosive forward Jeff Green, savvy rookie big man Jared Sullinger and Darko Milicic, a veteran center Rivers believes will contribute even though Milicic never turned into the star many thought he could be.

The Celtics get no break in the season opener Tuesday when they go on the road to play the defending champion Miami Heat, the team that eliminated Boston in the Eastern Conference semifinals in 2011 and the conference finals last season.

The rivalry – the best in the league right now – burns hotter, more contentious than ever after guard Ray Allen’s decision to sign with (some say defection to) Miami in July. Garnett said early in training camp he discarded Allen’s phone number.

With the modern-day Big 3 of Garnett, Allen and forward Paul Pierce broken up, the Celtics have a dramatically … [For more on New-look Celtics warm up to challenge of toppling Heat, click here.]