She admits that she was not at her best against the 22-year-old but says that finding a way to win is the most important thing.
"Tennis is not really about [getting back to my best]. It's about winning when you're not at your best," Williams told Eurosport after her match.
"Some days I play amazing and other days not so much, today was one of those days and it's about winning those games.
"I do look at the draw so I know I'm playing Maria. I will need to bring my best game if I want to win that one."
Sharapova has come through both of her matches so far without dropping a game, but insisted that she just wants to win.