She has been in the top 10 since 2012 .
Kerber , then ranked No. 91 in the world , had had a breakthrough event at the U.S. Open in 2011 , when she lost to eventual champion Sam Stosur in the semifinals .
Kerber has been in the top 10 since 2012 .
Kerber , then ranked No. 91 in the world , had had a breakthrough event at the U.S. Open in 2011 , when she lost to eventual champion Sam Stosur in the semifinals .