When the Knicks and the Celtics met in the first round of the 2011 playoffs, they didn’t play at Madison Square Garden until Game 3. By that point, the Celtics had a commanding 2-0 lead and went on to sweep the series with a pair of blowout wins in New York. Things will be much different when the long-time rivals square off tomorrow. For starters, the second-seeded Knicks earned the chance to set the tone by securing home-court advantage. “That was our goal — to lock down home court,” Knicks forward Carmelo Anthony said. “We did that, and now we have the opportunity to do something special. It won’t be easy, but we’re up for that challenge. It starts Saturday and the good thing about that is we’re here on our home court and we have a chance to protect that.” Home-court advantage is one of many changes from the previous playoff meeting. The Knicks roster has undergone a complete makeover since Anthony was acquired in a blockbuster trade with Denver midway through the 2011 season. With Amar’e Stoudemire sidelined by a knee injury, Anthony is the only active player remaining from the team that got swept by the Celtics, who themselves return only Kevin Garnett, Paul Pierce and Jeff Green. “We’re different as a team,” said Anthony, who led the NBA in scoring with 28.7 points per game. “As an organization, we’re a lot different than we were a year and a half, two years ago. The mindset is a lot different. My mindset right now is a lot different.”