Argentina flyhalf Juan Martin Hernandez could miss the Rugby World Cup after seriously damaging his knee while playing for his club Racing Metro in the French league.
Racing said on Monday that Hernandez tore his right anterior ligament in a match against Bourgoin on Saturday and will undergo an operation soon.
Hernandez is likely to be out of action for at least six months.
Argentina starts its World Cup campaign on September 10 against England.
Hernandez said on his personal website that he will "do the impossible" to play at the tournament in New Zealand.