ROME, Oct 6, 2008 (AFP) - Inter Milan defender Nelson Rivas faces surgery this week on the right knee injury he picked up in Saturday's Serie A game against Bologna.

Inter, announcing the news Monday, gave no indication as to how long the 25-year-old Colombian would be sidelined.

Rivas is the club's fourth defender to suffer injury after Italian World Cup winner Marco Materazzi (thigh), Cristian Chivu and the Brazilian Maxwell.