Following a detailed scan on Monday evening, the club can announce that Stuart Holden has been diagnosed with a torn anterior cruciate ligament in his right knee.
The midfielder, who recently agreed a contract extension with Wanderers, sustained the injury representing the USA in the final of the CONCACAF Gold Cup against Panama on Sunday evening.
The-28-year-old, was forced off the field of play in the 24th minute, with Jurgen Klinsmann's side eventually going on to win the game 1-0.
Holden will now consult with both the club's and the national side's medical staff to formulate a treatment plan.
Head of sports performance Mark Leather said: "We've got the scans and the results will be analysed by our specialists. We can then put an action plan in place over the next week to ten days when the initial swelling reduces."