Angelique Kerber. Pic/AFP
Angelique Kerber. Pic/AFP

Angelique Kerber displaced Serena Williams at the top of the WTA rankings released on Monday. Kerber had assured her place as world number one by her performances in the Madrid Open last week. The German, made it to the third round where she faced Eugenie Bouchard and retired with a lower back injury trailing 6-3, 5-0.