Top - ranked Rafael Nadal extends his unbeaten run on clay to 31 matches . Spaniard sets up quarterfinal match with seventh seed Gael Monfils in Barcelona . Former world Swiss has to play Jurgen Melzer in rematch of Monte Carlo semifinals . Last year 's runner - up Sam Stosur beats women 's No . 3 Vera Fischer in Stuttgart .
Top - ranked Rafael Nadal extends his unbeaten run on clay to 31 matches . Spaniard sets up quarterfinal match with seventh seed Gael Monfils in Barcelona . Swiss has to play Jurgen Melzer in rematch of Monte Carlo semifinals . Last year 's runner - up Sam Stosur beats women 's No . 3 Vera Fischer in Stuttgart .