Pato may have been the match-winning hero in AC Milan's 2-1 Italian Cup victory over Novara on Wednesday but a day later he discovered he will face up to a month on the sidelines.
Pato has been injury prone over the last two and a half seasons and he has suffered yet another problem having been diagnosed Thursday with a slight hamstring pull.
Milan said he faces three to four weeks out.
Having scored the winner 10 minutes into extra-time against Novara, he was forced to leave the field in the second extra period after feeling a problem in his hamstring.
What makes it even worse is that the vast majority of his injuries have come at Milan's San Siro stadium, whose pitch is often criticised for its poor state.