The top-ranked Williams took the last six games and added to her championships on the red clay of Roland Garros in 2002 and 2013.
In a riveting showdown 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.
The four-time Grand Slam champion lost to 18-year-old Laura Robson of Britain in the second round of the U.S. Open on Wednesday, and will head into retirement after she finishes playing in doubles at Flushing Meadows.
Top-ranked Victoria Azarenka withdrew from the Rogers Cup on Friday because of a knee injury, but she hopes to be ready for the U.S. Open.
After a day full of lopsided mismatches at the U.S. Open, we have yet another. But this one’s an upset.
American teenager Madison Keys showed her youth late in her second-ever match at a Grand Slam tournament, repeatedly blowing leads in a loss to 27th-seeded Lucie Safarova at the U.S. Open.