Manchester United's on-loan winger Bebe could be sidelined for six months after tearing his anterior cruciate ligament playing for Portugal under-21s.
The 21-year-old joined United from Vitoria de Guimaraes for £7.4m in 2010, but has played only seven first-team games for the Premier League champions.
In June United agreed a one-season loan deal for the player with Besiktas.
The Turkish club have contacted United to discuss where the operation on his left knee should take place.
Bebe was injured playing for Portugal under-21s in Slovakia on Tuesday night.