The Celtics yesterday set up shop in the visitors locker room at the Pepsi Center with an intrigued newcomer sitting on the floor in front of a video screen while his new teammates got dressed. Terrence Williams, about to sign a 10-day contract with the Celtics, is still waiting for his release from the Guangdong Southern Tigers of the Chinese League to be finalized. As such, he was happy to quietly watch. It’s another fresh start for the No. 11 overall pick (by New Jersey) in the 2009 NBA draft. He’s since played for the Nets, Rockets and Kings, and been cut at the end of training camp by the Pistons before heading to China last fall. Though the athletic swingman from Louisville hasn’t stuck for long in any one place, he’s landed in a locker room with a better record than most of accepting players into the fold. “We’re patient. We have a lot of veteran leadership here, and we root for each other,” said Kevin Garnett. “That’s not the case on all teams. Not every guy is for each other even though they say they are. That’s not the case around the league. But every guy in here is for each other. We run like a pack. We’ve had some guys not buy in since I’ve been here. But for the most part the encouragement and influence is there for young guys. All you can ask is for the rooting. “Always good to see a young guy come in and get another chance. I’ve always been a big fan of T-Will, so it’s good to see that he’s here.” Garnett’s message to Williams will be simple. “My message is play together and play unselfishly. Nothing more or less,” he said. “But everyone in here follows the leadership of the guys here. We share the ball, we get guys open, we encourage, we promote. We root for the next person, because that’s what it is. The mentality here is like a pack. We play as a pack, fight as a pack and survive as a pack.”