Maria Sharapova has been knocked out of Wimbledon by a 131st-ranked qualifier on a day when injuries forced the withdrawal or retirement of seven other players.

The third-seeded Sharapova, the Wimbledon champion in 2004 champion, lost 6-3, 6-4 to Michelle Larcher de Brito of Portugal in the second round at the All England Club.

It's the second significant upset of the tournament, which is only in Day 3. Two-time men's champion Rafael Nadal was beaten on Monday by 135th-ranked Steve Darcis.

Sharapova slipped and fell several times on the grass on Court 2 and received medical treatment from the trainer in the second set.

The women's tournament also lost second-seeded Victoria Azarenka, who withdrew before her match with a knee injury. Sharapova and Azarenka had been considered the main challengers to five-time champion Serena Williams.