Russian former Wimbledon champion Maria Sharapova was made to work as she downed Barbora Zahlavova Strycova in straight sets to reach the fourth round on Saturday. Sharapova booked a fourth round clash with title holder Serena Williams by beating the Czech number five 7-5, 6-3 in an hour and 54 minutes on Court One. The former world number one turned up the volume in her battle with the Zahlavova Strycova, grunting loudly as she hit the ball. Sharapova had three match points and won the contest with an ace. 'It's great to be in that second week. It always means you've won a few rounds and the tougher ones are ahead of you,' the 16th seed said. Looking forward to her round of 16 clash, she added: 'It'll be a really tough match. She's a defending champion and playing really well.' 