(CNN) -- World No. 1 Caroline Wozniacki is looking to win her first grand slam crown. Maria Sharapova, one of her predecessors as the top women's tennis player, is returning to the scene of her breakthrough title. Both players are adamant that their biggest obstacles to success at Wimbledon this year will be the Williams sisters Serena and Venus. The Americans are back on the scene after varying but significant absences. Serena, a four-time champion at the English grass-court grand slam, is playing just her second tournament since winning last year's final -- her second triumph in a row in south-west London.
@highlight
Serena and Venus Williams are the players their female rivals hope to avoid at Wimbledon
@highlight
American sisters have won the grass-court grand slam nine times between them
@highlight
World No. 1 Caroline Wozniacki is drawn to potentially meet Serena in semifinals
@highlight
Maria Sharapova, the 2004 champion, is in the same half of the women's draw
Sharapova, who stunned @placeholder as a 17-year-old in the 2004 final, is wary of the Williams' vast experience at the tournament.