Palermo limped off in the second half of defending champion Boca's 3-1 loss to rivals River Plate on Sunday.

"I'm going to be out for one month and a half," he told radio network La Red on Monday. "I'm relieved it doesn't require surgery but angry because I'm going to miss the next games."

Palmermo has scored six goals in nine games in the Apertura championship, two behind leading scorer Daniel Montenegro of Independiente.

Boca won both championships played in the 2005/6 season but have struggled to adapt since Ricardo La Volpe took over as coach last month.

La Volpe replaced Alfio Basile, who was named the new coach of Argentina. When La Volpe took charge, Boca were unbeaten since February and had won their last 12 games.

Boca lead the Argentine championship with 22 points from nine games, one ahead of River who have played a game more.