Pirlo was originally ruled out for two to three weeks after suffering the injury in his left leg and hopes to be fit for the third group game against Slovakia.
Pirlo has already been subjected to a series of cures to help the muscle recover more rapidly.
These include laser treatments, hyperthermia treatment induced by microwave diathermy and Tecar therapy.
Gazzetta dello Sport says the latest system used to help Pirlo's recovery is ARP Wave.
This is a form of electrotherapy that sends a current deep within the tissues being treated.
The system has been used by both Milan and Fiorentina.