Jason Terry became a Celtic last summer because he believed the team represented his best chance at winning a second NBA championship. A devastating mix of problems, from injuries and age to Terry’s own subpar performance, got in the way last season. But the 35-year-old guard, who had arthroscopic surgery to remove the plica from his left knee two weeks ago, doesn’t believe the overall team goal has changed. Danny Ainge is weighing the futures of Paul Pierce and Kevin Garnett, and Doc Rivers is giving serious thought to not coming back, but Terry insists that he’s still in the right place. Or at least he hopes so. “Things haven’t changed — not at all,” he said recently. “My understanding is that we’re still trying to win a championship. What moves they make in the offseason is on them. But my goal is to play at the level we need to win a championship.” Rivers hasn’t discussed his future with anyone at the team’s training facility in Waltham but has talked with Terry about other matters. “I haven’t talked to him about anything personal,” said Terry. “We talk about next season, and what I have to do moving forward.