Pato broke down - again - in Milan's Champions League defeat at Barcelona.
"Alexandre is sad at his latest injury, but hopes to be back soon, because he is very fired up," agent Gilmar Veloz told TMW.
"We have to hope for the best and he will undergo tests tomorrow. Why does he have so many injuries? That is something you'd best ask the Milan medical staff, as I wouldn't know what to say."
So close to joining Paris Saint-Germain in January, it is widely reported that Pato will resume talks with the French club over the summer.
"Let's just leave him to think about healing now..."