The Celtics started the All-Star break yesterday hungrily, like someone crawling into bed after a very long week. In their case, at 28-24 and seemingly getting better, it’s been a long 52 games. Paul Pierce has been playing with a pinched nerve in his neck. “The last two weeks it’s been better,” said the Celtics captain with a solemn nod, because winning always helps the pain. Kevin Garnett, seemingly out of the blue, talked of the 14th All-Star appearance of his career on Sunday in Houston being his last, though the Celtics center didn’t carry the comment a step further, and make it a retirement declaration. “Ya’ll don’t know what I know,” he said. Danny Ainge yesterday downplayed Garnett’s words, saying he has never had that conversation with the Celtics center. Ainge suggested that the comments stemmed from Garnett’s state of mental exhaustion. “Kevin was very tired after that game,” he said of the Celtics’ Wednesday night win over Chicago, their eighth in the last nine games. “He has been grinding for us every night. He’s one of the people who has been carrying us, and he gives everything. When you’re in that frame of mind, sometimes those thoughts can occur.” Outside help is clearly in order. Ainge hopes to sign one and possibly two players, perhaps by the time the season resumes Tuesday night in Denver. The losses of Rajon Rondo, Jared Sullinger and Leandro Barbosa demand it. Ainge’s active players demand it, too.