The American has not yet dropped a set in Melbourne, but said that she must be "focused" against the 14th seed if she is to make the last eight.
"Maria [Kirilenko] is playing consistent tennis, especially the past 16, 18 months, she's been so consistent," said Williams. "So my goal is just to be really focused against such a player that's doing so well."
Williams was asked about a potential final against in-form Maria Sharapova, but stopped short of making any bold predictions.
"She's playing great," she added. "I think she's doing everything well.
"I have to get there. I have three more matches to win. I can't worry about that right now. I just have to take everything a step at a time."
The world number three has lifted the title in Melbourne on five previous occasions - the last coming in 2010.