Australia's Samantha Stosur reached the quarter-finals of the French Open on Sunday with a 7-5, 6-4 win over Sloane Stephens of the United States.
The US Open champion, seeded sixth, will play Dominika Cibulkova of Slovakia for a place in the semi-finals.
Stosur, who was the losing finalist here two years ago, was expected to be too strong and have too much big game experience for the young American, but she struggled to impose her game in the first set.
The 19-year-old Stephens, playing in just her fourth Grand Slam tournament and into the fourth round for the first time, broke to lead 4-3 and then held serve for a 5-3 lead.
Two games later she served to go a set up, but Stosur turned up the power just when she needed it to break back.
The Australian won the next two games to take the set 7-5, breaking to love in the 12th game.
The second set was more one-sided with Stosur breaking early and powering away to reach the last eight.
The defeat for Stephens means that Uzbekistan-born Varvara Lepchencko is the lone American left in the tournment following the early departures of the Williams sisters and the failure of the US men to get one player past the second round.
Lepchencko goes for a quarter-final place on Monday with a match against fourth seed Petra Kvitova of the Czech Republic.