The Celtics will do what they can to reconfigure their roster this summer and begin next season with a team they believe can be competitive. But that most likely won’t be enough. As the Celts learned this year, what your rotation looks like in April and May can be radically different than that which you put on the table in November. You need to either be lucky enough to avoid major injuries — and even the smaller ones that change the productivity of key players — or fortunate enough to have the right replacement types (an even harder proposition in this thinned out NBA). Bringing this back to Boston, you’re still not going to beat what Miami has become if you add Rajon Rondo, Jared Sullinger, Leandro Barbosa and even big body Darko Milicic to the final crew. But you’re still in the playoffs. Even before the playoff series with New York had ended, president of basketball operations Danny Ainge was using perspective as he took stock of the 2012-13 campaign. “To be honest with you, I’ve enjoyed watching our team play this year,” Ainge said. “I’ve enjoyed it. I mean, we’ve had some down times and some struggles, but I’ve enjoyed our guys. I think our coaches have done a magnificent job coaching this team. “I think it just wasn’t the team that we envisioned starting the season. Like, Darko had a tremendous preseason, and Jared looked amazing and proved to be a major, major factor.