The Ghana international played a key role in sealing the Rossoneri's place in the Champions League group stages earlier this week but is now set to return to Germany
The Ghana international hinted at a return to Germany earlier this month, admitting that he was open to the idea of being reunited with Jurgen Klopp at Borussia Dortmund.
However, the former Hertha Berlin ace is now set to link up with Schalke, with die Knappen taking to Twitter on Friday morning to announce that a deal was imminent.
"Kevin-Prince Boateng is in Gelsenkirchen for a medical check - S04 are about to sign him!"
Boateng's surprise San Siro departure will only intensify speculation that Milan are set to re-sign former idol Kaka, who expressed his wish to leave Real Madrid on Thursday evening.
However, the Rossoneri have also been trying to bring forward the arrival of CSKA Moscow playmaker Keisuke Honda, who has already agreed to move to the Giuseppe Meazza on a free transfer in January.
Boateng, who was born in Germany but represents Ghana at international level, joined Milan from Portsmouth via Genoa in 2010.