DENVER — To hear Jason Terry talk about him, the Celtics aren’t getting a run-of-the-mill, 10-day guy in Terrence Williams, a fellow Seattle native. “I know him well,” Terry said of the 6-foot-6, 220-pound guard, who is expected to be signed to a 10-day contract. “He’s one of the young kids who grew up in that area that had tremendous talent. He’s a freakish athlete. When you talk about athleticism, he’s right there with LeBron (James) and (Kevin) Durant and these guys that are high flyers. He’s right up there with him.