In Australian Open Tennis, after the shock exit of world number one Andy Murray, top seed in the Women's Singles, Angelique Kerber has also been knocked out in the fourth round. The German, who was the defending champion, was stunned by an unseeded American Coco Vandeweghe, in straight sets 2-6, 3-6. Murray had lost to 50th ranked German Mischa Zverev.Meanwhile, World No 2 Serena Williams has stormed into the Australian Open quarter-finals joining sister Venus with a straight-sets 7-5, 6-4 win over 16th seed Czech Barbora Strycova. Earlier Venus Williams became one of the first to reach last eight after beating German qualifier Mona Barthel 6-3, 7-5. She will meet Anastasia Pavlyuchenkova in the quarter-final.35-year old Swiss, Roger Federer, however, fought his way closer to an 18th Grand Slam title as he made it to the quarterfinals with a five-set win over Kei Nishikori. The Swiss won the last of his record 17 Slam titles in 2012. In Mixed Doubles, Leander Paes and Martina Hingis will play their pre-quarterfinal match today. Sania Mirza and Rohan Bopanna, with their team-mates, will play their Mixed Doubles last-16 games later in the tournament.