The two strikers swapped clubs on two-season loans on the final day of the summer transfer window and at first Rebic struggled to make an impact at San Siro.
The change of tactical system has brought the best out of him, scoring five goals in his last five Serie A appearances.
It’s reported the Rossoneri are now working on a permanent transfer for the Croatia international and Eintracht Frankfurt are open to negotiations.
“As the transfer was done minutes before the deadline, we didn’t have time to agree any kind of set purchase option or figures,” director of sport Hubner told Kicker.