That puts Williams in an exclusive club with 10 other women: Martina Navratilova, Chris Evert, Steffi Graf, Virginia Wade, Arantxa Sanchez Vicario, Lindsay Davenport, Conchita Martinez, Evonne Goolagong Cawley, Billie Jean King and Venus Williams.
One more victory and she ties big sister Venus, who has 651 career wins.
Suarez Navarro, who leads the WTA in matches won (28) this season, entered the match with a 0-3 record against Williams. She had only won five games in six sets.
But yesterday she was at home, in her native Spain, and on her best surface. Fresh off her first WTA title win in Portugal, the 15th-seeded Suarez Navarro's defense proved puzzling for Williams at first.
Shots that would have been winners against most players were batted back by Suarez Navarro, who's built her career on counter-punching. Williams got off to a shaky start, giving up the break in the opening game. However, Suarez Navarro's defense slowly succumbed to Williams' aggressive play.
Williams adds this milestone to a growing list of career accomplishments. Last year, she became the oldest woman to hold the WTA No. 1 ranking. She finished the year with a record $12.4 million in prize money. She has earned more prize money than any woman in the history of the tennis.
She's also earned more prize money than any American tennis player, male or female. She set the record for career prize money earned by a female athlete back in 2009, surpassing golfer Annika Sorenstam. Williams is the only female athlete to top $50 million in career prize money.
Next, Williams faces No. 5 seed Petra Kvitova, who defeated Lucie Safarova, 6-4. 6-3. A two-time defending champion in Madrid, Williams is shooting for her 60th career WTA title.