The Ghana international is racing against time to recover ahead of their Europa League game on Thursday
The defender injured his right knee during the match against Rio Ave over the weekend and was replaced during the first half.
“The player David Addy is being reassessed by the medical department of Guimarães and it is not clear that he can be fit for Thursday’s Europa League game,” coach Rui Vitoria told Maisefutebol.
“The 23-year-old guardsman has failed the first two workouts this week but we are doing all we can to make him fit by Thursday.”
Luís Rocha could earn his debut this season in the Europa League should Addy fails to recover.
Their group also includes Spanish La Liga side Real Betis and former French champions Olympique Lyonnais