Williams ran her winning streak to a career-high 24 matches with a 6-1, 6-3 victory Sunday over Victoria Azarenka at the Italian Open.
It was the fifth title this year for Williams, whose 51 WTA championships are sixth-most all-time. Monica Seles (53) is fifth on that list and Lindsay Davenport (55) is fourth. All are far behind the top three on the all-time list: Martina Navratilova (167), Chris Evert (157) and Steffi Graf (107)
The French Open seedings and draws are to be announced this week and Williams will be a prohibitive favorite. She's won the French Open once -- she's claimed each of the other Grand Slam events at least four times each -- but is 33-1 on clay courts since the 2012 clay-court season. That loss was a first-round defeat in the 2012 French Open.
Williams has 11,620 points, increasing her lead over No. 2-ranked Maria Sharapova, who has 10,015 points. Azarenka is third at 9,005.
Agnieszka Radwanska is fourth at 6,475 but is sitting out this week to rest an injured shoulder ahead of the French Open
Errani improves a career-high No. 5 ranking after reaching the semifinals of the Italian Open, pushing Li Na down one spot to sixth. Errani has 5,835 points to Li's 5,335.
The rest of the Top 10 also shifts with Petra Kvitova (5,175) up one place to seventh, switching places with Angelique Kerber (5,135). Samantha Stosur, with 3,645 points, again changes places with Caroline Wozniacki (3,625), taking the ninth spot and leaving Wozniacki 10th.
Wozniacki, who leads the field at the Brussels Open, is the only Top 10 player in action this week. No. 14-ranked Marion Bartoli is the top seed for this week's WTA tournament in Strasbourg, France.