The Celtics also dealt three-time slam dunk champion Nate Robinson to the Thunder and received a 2012 first-round draft pick and cash in the deal that was approved by the NBA about five hours after the trade deadline. The draft pick was previously owned by the Los Angeles Clippers.
Perkins recently returned from a knee injury he sustained in Game 6 of the NBA finals. Once loaded with interior size, the Celtics will now have to hope Shaquille O'Neal or Jermaine O'Neal get healthy in time for the playoffs.
"We need to get Shaq healthy. Shaq will be healthy. But if Shaq plays great, then this deal was obviously really, really good for us," coach Doc Rivers said. "And that's on Shaq. Getting Shaq in great shape, getting him ready, getting him healthy is really going to be important for us in the playoffs."
The Thunder parted with Green, their third-leading scorer who frequently played out of position at the power forward spot, and the 7-foot Krstic for the chance to get the key interior defender they had been lacking. General manager Danny Ainge called him an "integral" part of Boston's championship run three seasons ago.
Perkins could team with second-year pro Serge Ibaka in a revamped frontcourt to go along with high-scoring All-Stars Kevin Durant and Russell Westbrook. Oklahoma City sits fourth in the West, and general manager Sam Presti said it is "never easy to make decisions such as these."
"We had a unique opportunity to add a proven presence in our front court in acquiring Kendrick," Presti said. "He will help anchor our defense while Nate will add depth and athleticism to our backcourt."
The versatile Green can be a backup at multiple positions and fill the void Boston created by trading away injured swingman Marquis Daniels to Sacramento.
"We've been trying to get that lineup since Posey left. And I think people forget how many times we did that in the playoffs, which was every fourth quarter for the most part," Rivers said. "We haven't been able to duplicate that."
Green's production dropped off after he missed seven games early this season with a sprained left ankle, but he was starting to break out of it recently. He had been averaging just 13.7 points over a 29-game span, but surpassed 20 points in four of his last 10 games leading up to the trade deadline.
"That's ironic that now we're a team of continuity and consistency," said Heat coach Erik Spoelstra, as Miami was the only one of the top six East teams without some tinkering around the trade deadline.
The inclusion of Krstic, the Thunder's starting center since they brought him back to the NBA from Russia in December 2008, should help offset Boston's loss of Perkins. Krstic had been out of the league after suffering a knee injury with New Jersey.
"He's really appreciative of the opportunity Oklahoma City gave him. They really gave him a second chance coming out of Russia into the NBA," Krstic's agent, Marc Cornstein, said. "He's excited about going to Boston and to hopefully bring them a title."
In a separate deal, Boston got a second-round draft pick from the Cleveland Cavaliers for reserves Luke Harangody and Semih Erden for a total of five Celtics players departing.
"It's always going to have an effect on chemistry, when you take away guys, you add guys," guard Delonte West said. "At the end of the day, we're still professionals. We've got to be basketball players. Somehow, some way, we have to make it work."
Oklahoma City also added frontcourt depth by acquiring backup center Nazr Mohammed from Charlotte in exchange for seldom-used forward D.J. White and veteran guard Morris Peterson, who had played in only four games this season.
"Tough day for me and my teammates ... good luck to jeff green, nenad krstic, (Peterson) and Dj white," Durant posted on his Twitter account. "we will miss u guys 4 sure."
The Thunder had been looking for an upgrade to their interior defense and Perkins, 26, could provide it while fitting in with a youthful roster. His contract expires at the end of the season, but Oklahoma City faced the prospect of losing Green and Krstic then anyway.
Green will be a restricted free agent and didn't agree to an extension last summer, when Durant signed a long-term deal. Westbrook's contract also comes up this summer, leaving Oklahoma City with some difficult financial decisions to make.
Green had been a part of Oklahoma City's core, coming over in a 2007 draft day trade that sent Ray Allen to Boston and set the stage for the Celtics' championship run. The Thunder, then in Seattle, also picked Durant at No. 2 the same day.