BUENOS AIRES, March 10 (Xinhua) -- Sao Paulo striker Alexandre Pato has criticized a contract clause that prevents him from playing against local rivals Corinthians.

The 25-year-old, who joined Sao Paulo on loan from Corinthians last year, said the proviso breached the spirit of the game.

"It's sad not to be able to play," the former AC Milan striker told reporters.

"It's such a special match that means so much to fans of both clubs. These contractual clauses are not what football is about. You don't see it in Europe.

"For the good of the game and the spectacle, players should be free to play. But it's something we have to accept."

Pato has already missed two matches due to the stipulation this year.

The next time he will be forced to watch from the sidelines will be the teams' final Copa Libertadores group match on April 22.

Pato is in the final season of a two-year loan deal from Corinthians, who bought the striker from AC Milan for 15 million euros in January 2013.

He has scored eight goals and provided two assists from 10 matches so far this year.