Serena Williams says that she believes that her older sister Venus will return to the tour. Venus, 31, has not played since the U.S. Open after she was diagnosed with the autoimmune disease Sjogren's syndrome.

"She made a great effort [to play the Australian Open]," Serena said. "I saw her training every day next to me. I was a little shocked she didn't come. That just means she's preparing for another event. She'll be out really fast. I told her that she has to take care of herself first. She's like, 'Yeah, I know, I'm feeling good.' She's doing better now that she knows what she's going through, she knows how to treat it, and it's working a lot better for her."