WATCH: Stosur continues her fine form in Paris
SAM Stosur's imposing French Open march rolls on.
The Queenslander reached the fourth round at Roland Garros for the sixth time from 14 attempts with a powerful 6-2 6-2 victory over American Bethani Mattek-Sands on Friday night.
The 2010 finalist and a semi-finalist on three other occasions, Stosur is yet to drop a set this year.
Seeded 23rd, Stosur will take on Jelena Ostapenko after the Latvian's 6-1 6-4 destruction of Ukraine's Lesia Tsurenko.
The Gold Coaster has now won eight claycourt matches in succession.
Stosur made a blinding start, racing to a 3-0 lead inside 10 minutes when a nervous Mattek-Sands dropped service twice.
Stosur surrendered one of the breaks before claiming a third breach of the Mattek-Sands' serve to seal the first set in 31 minutes.
The pattern continued into the second set with a fourth break in the opening game, but a fired up Mattek Sands immediately broke back.
Stosur regained control after an eight-minute third game as frustrated Mattek-Sands shoved a forehand wide.
Steaming towards victory at 2-1 (40-15), Stosur inexplicably lost her way as rain fell.
But the American again failed to capitalise, losing serve for a fifth time.
Stosur was simply too accomplished, taking only 70 minutes to progress with nine winners and only 14 unforced errors.
She was lethal on return, converting seven of 11 break points.
Defending champion Garbine Muguruza still looms large in Stosur's second-week pathway.
The Spaniard wore down Kazakhstan's Yulia Putintseva 7-5 6-2.
Stosur's likely quarter-final opponent, should she reach that stage, will be either former champion Svetlana Kuznetsova or ex-world No 1 Caroline Wozniacki.