She had won 19 matches in a row when she ran into German phenom Angelique Kerber in the quarterfinals of the 2012 Cincinnati Western & Southern Open. Kerber is a powerful lefty who has rocketed up the ranking in 2012 and reached two major semifinals in the last 12 months (2011 US Open and 2012 Wimbledon). However, Kerber's lefty serve gave Serena fits today, and was able to take advantage of shocking errors by Serena to win 6-4 6-4. The German blew two match points but then was able to finish the match with an ace.
Venus Williams was able to win her quarterfinal match against 2011 US Open champion Samantha Stosur in 3 tough sets 6-2 6-7(2) 6-4.