Bolton Wanderers have confirmed that Stuart Holden is likely to be out for between six and nine months following a knee operation.
The American, who has already missed seven months of football with a cruciate ligament injury, lasted just 23 minutes in an Under-21 match last week.
Following tests, Holden had an operation on the ligaments in his right knee, and is now set for another spell on the sidelines.
The 28-year-old joined the Trotters in 2010.