Wimbledon 2012: Serena Williams confident of stepping up game and defeating champion Petra Kvitova Williams has won both previous encounters between herself and Kvitova, with the most recent one coming in 2010 when the American prevailed in straight sets at the semi-final stage of Wimbledon. Kvitova coasted through her second-round and third-round matches but was made to fight for her 4-6, 7-5, 6-1 win over Francesca Schiavone yesterday and is now relishing the prospect of facing 13-time grand slam champion Williams. "It will be a huge match for both of us, and I'm looking forward to the challenge of playing against her," the Czech said. She has played well and she is a great champion. She's won many times here. I will try my best and we will see what happens. Germany's Sabine Lisicki pulled off the biggest upset in the women's singles yesterday when she knocked world No 1 Maria Sharapova out at the fourth-round stage. Lisicki's reward is a last-eight clash against compatriot Angelique Kerber on Centre Court. Lisicki, the 15th seed, is being tipped by some to win Wimbledon after her 6-4, 6-3 win on Court One, but she insists she will keep her feet firmly on the ground. "You have to take it match by match," she said. I've been playing better with each match and I have been playing better each year, so we'll see where I end up. Weather permitting, second seed Victoria Azarenka will take on Austria's Tamira Paszek and third seed Agnieszka Radwanska faces 17th seed Maria Kirilenko. Women's singles quarter-final line-up: (6) Serena Williams (USA) v (4) Petra Kvitova (Cze) (15) Sabine Lisicki (Ger) v (8) Angelique Kerber (Ger) (3) Agnieszka Radwanska (Pol) v (17) Maria Kirilenko (Rus) Tamira Paszek (Aut) v (2) Victoria Azarenka (Blr)