Ibrahimovic is to undergo medical tests today after breaking down in training yesterday. Initial reports suggested an Achilles tendon injury.
Gazzetta dello Sport says should the tests show a serious injury, Milan could release Ibra from his contract.
And should he become a free agent, a return to Sweden with Hammarby will be on the cards.
Ibrahimovic is a part-owner in the Allsvenskan club.