France's [Images] Richard Gasquet has pulled out of the French Open with a knee injury, organisers said on Monday.

The French number one, who was seeded eighth, injured his left knee and will have a scan later in the day.

"Gasquet has withdrawn because of a sudden blockage of his left knee," organisers said in a statement.

Gasquet, who was scheduled to play compatriot Florent Serra in the first round on Monday, has been replaced in the draw by Colombian Santiago Giraldo.

The 21-year-old Gasquet has had a disappointing season so far, winning 10 matches and losing as many, prompting a change of coach last weekend.

Organisers added that German Florian Mayer, who was due to play Frenchman Fabrice Santoro, also withdrew because of gastro-enteritis. He will be replaced by Russian Evgeny Korolev.