The 24-year-old has not played since late September and his spell on the sidelines has now been extended.
U.S. international forward Aron Johannsson will be out for "the coming weeks" after undergoing hip surgery on Wednesday.
The Werder Bremen man has not played since Sept. 22 after initially suffering a groin strain at U.S. training camp earlier in September. The problem was later diagnosed as a nerve issue in his right hip, and he will now be sidelined several more weeks.
“We have exhausted all non-surgical treatment options and, unfortunately, could not sustain freedom from pain,” said Werder Bremen team doctor Dr.