Milan made the announcement on its website on Wednesday, saying the move is a temporary loan since Merkel’s rights are jointly shared by Milan and Genoa.
The 19-year-old Merkel made 10 appearances and scored one goal in all competitions for Milan last season. During the first half of this season, he played 14 times for Genoa.
Milan announced Boateng’s injury late Tuesday, adding that goalkeeper Christian Abbiati has a mild left calf problem.
Milan trails Serie A leader Juventus by one point.
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