MILAN, Nov. 12 (Xinhua) -- AC Milan striker Alexandre Pato is expected to be sidelined for six weeks after injuring his left hamstring in the midweek win over Palermo, the club announced on Friday.

The Brazil striker, who opened the scoring to help the Rossoneri to the Italian Serie A summit, picked up the injury after 65 minutes and was replaced by Filippo Inzaghi who subsequently suffered a season-ending knee injury a quarter of an hour later.

Pato underwent tests on Friday and a Milan statement confirmed "he will need six weeks to resume playing".

It means that Zlatan Ibrahimovic, Ronaldinho and Robinho are the only senior strikers available to Milan coach Massimo Allegri for the city derby against European and Italian champion Inter Milan on Sunday.

So far this season the 19-year-old Pato has scored six league goals to help Milan to the top of the Serie A.