ATLANTA — Braves outfielder Matt Diaz will be out at least a month after injuring his left knee attempting to make a catch.

Diaz underwent an MRI today that showed a partial tear in the posterior cruciate ligament. Team doctors estimate he will be out four to six weeks.

Diaz, hitting .250 with two homers and 14 RBIs, was injured in Tuesday night's game at Milwaukee while trying to make a diving catch in foul territory. He also sustained a cut below the knee that needed four stitches.

The Braves activated reliever Rafael Soriano after placing Diaz on the 15-day disabled list. The right-hander started the season as Atlanta's closer but missed 45 games with elbow tendinitis