Williams wasn't pleased with her two singles losses at the Hopman Cup team event in Perth, Australia, including in straight sets to Eugenie Bouchard, but said Saturday there is "a little light at the end of the tunnel."
"I'm never really happy about my practice or preparation," the top-seeded Williams said Saturday. "So maybe that's a good sign. I definitely feel better now than I did a couple weeks ago. But every day I can see something coming through."
Second-seeded Sharapova said that although she played well at Brisbane and had a "tough" final against Ana Ivanovic, "every week's a surprise."
"You can't be overly negative; you can't be overly positive," Sharapova said Saturday. "I wanted to start off well. I thought I did many things well. But I'm not going into next week throwing flowers at myself or anything. I'm starting from scratch. I'm hungry. I'm determined to do better."
Williams also exited last year in the fourth round, losing to Ivanovic.
"Last year I felt really good, was playing well … feeling amazing on the court," Williams said. "This year I feel a little off. But I feel off in every Grand Slam. Last year, that didn't work out for me, so maybe this is different."
In the men's tournament, top-ranked Novak Djokovic is vying for his fifth Australian Open title, an accomplishment that would raise his overall number of Grand Slam event trophies to eight.
The 27-year-old who became a father in October arrived in Australia feeling ill and canceled a practice session Saturday, raising concerns about his fitness for the season's first Grand Slam tournament. But Sunday he was back on the court for a training session, hitting hard and moving well around the court, and said he was feeling better.
"I had a tough couple of days. But it's all behind me now. I'm ready for the Open," he said, adding he had picked up a virus in the Middle East where he played matches recently in Abu Dhabi and Doha, Qatar.
"[It was] a little bit of flu and stomach," he said. "But now it's good, it's passed."