Petra Kvitova of the Czech Republic. Photo: Christophe Ena/AP

Petra Kvitova's French Open comeback ended in the second round on Wednesday as she was knocked out in straight sets by American qualifier Bethanie Mattek-Sands.

The two-time Wimbledon champion was appearing in her first tournament since a horrifying knife attack at her home in the Czech Republic in December but lost 7-6 (7/5), 7-6 (7/5).

Mattek-Sands, the world number 117, will face 2010 Roland Garros finalist Sam Stosur of Australia for a place in the last 16.