Sources: Celts get Thunder's Jeff Green

Just before Thursday's 3 p.m. ET trade deadline, the Boston Celtics agreed to ship center Kendrick Perkins and guard Nate Robinson to the Oklahoma City Thunder for forward Jeff Green and big man Nenad Krstic, two league sources said.

Celtics director of basketball operations Danny Ainge said Wednesday that Perkins is out at least a week after spraining the medial collateral ligament in his left knee.

It's a homecoming of sorts for Green. He was selected by the Celtics in the first round (fifth overall) in the 2007 draft. But he was traded with Wally Szczerbiak, Delonte West to the then Seattle SuperSonics for Ray Allen and Glen Davis.

The Celtics' pursuit of a perimeter player intensified when it became apparent that Marquis Daniels might miss the rest of the season with a spinal injury.

The deal gives the Thunder the big man that they've been looking for all year. Perkins is coming off right knee surgery and has played just 12 games, but the Thunder have felt for a while that they need a veteran big man to truly compete with the Spurs, Mavs and Lakers in the West.

The deal also gives the Thunder something for Green, who becomes a restricted free agent this summer. Green had rejected a contract extension offer from the Thunder earlier this year.

For the Celtics, they take a big risk that their lone big men -- Shaquille O'Neal, Kevin Garnett and Krstic -- can lead them. But with O'Neal out with an Achilles injury, this is an interesting play for a Celtics team trying to win a championship.

Green is a young talent who can play both the 3 and the 4 positions and could be part of a longer rebuilding strategy. Krstic is an offensive talent down low, but isn't known as a rebounder or a tough defender.