Chicago Fire winger Patrick Nyarko suffered a torn ACL and sprained MCL in his right knee during Saturday's 2-1 loss to D.C. United, his club confirmed on Wednesday.
Nyarko, 28, will undergo surgery and be sidelined for about six to eight months.
The Ghanaian, who has played for Chicago since being drafted out of Virginia Tech in 2008, already missed three months this season with a knee sprain.
He only returned to the starting lineup earlier this month.
"Knowing the work he put in to get back and help us this season, we feel awful for Patrick," Fire coach Frank Yallop said in a statement. "We saw his return to form over the past few weeks and fully support him in his recovery efforts."