Serena Williams of the United States returns a shot in her Women's Singles match against Sloane Stephens of the United States on day nine of the 2015 French Open at Roland Garros on June 1, 2015 in Paris, France

Serena Williams of the United States returns a shot in her Women’s Singles match against Sloane Stephens of the United States on day nine of the 2015 French Open at Roland Garros on June 1, 2015 in Paris, France

*For the third match in a row at the French Open, Serena Williams dropped the opening set and had to hustle through two more to pull out a win.

Her latest victim – fellow American Sloane Stephens.

In a thrilling match between the last two American women in the draw, the No. 1-ranked and No. 1-seeded Williams came back to edge Sloane Stephens 1-6, 7-5, 6-3 and reach the quarterfinals at Roland Garros on Monday.

”Not simple for me today. I’m surprised to win,” Williams told the crowd in French. ”Experience helped me.”

Sloane Stephens of the United States returns a shot in her Women's Singles match against Serena Williams of the United States on day nine of the 2015 French Open at Roland Garros on June 1, 2015 in Paris, France

Sloane Stephens of the United States returns a shot in her Women’s Singles match against Serena Williams of the United States on day nine of the 2015 French Open at Roland Garros on June 1, 2015 in Paris, France

Williams managed to win despite 43 unforced errors, more than twice as many as Stephens’ 21.

As previously reported, Stephens ousted Serena’s sister Venus in the first round of the French Open.

Williams’ quarterfinal opponent will be No. 17 Sara Errani, a 6-2, 6-2 winner over Julia Goerges. Errani lost the French Open final in 2012, when Maria Sharapova completed her career Grand Slam.