Halep outplayed Serena’s older sister Venus in a 6-2 6-3 third-round victory, a performance she described as her best of the season but the Romanian knows Serena is the bigger obstacle.
“She was (intimidating) when I was younger but now I don’t feel intimidated anymore,” the 27-year-old told reporters.
“It’s going to be huge challenge for me. It’s always great to play against Serena because every time I have to learn something from the match.”
Halep has lost eight times in nine meetings with Serena, which all came before the American took time off around the birth of her daughter in September 2017.
Should Halep win on Monday, she will join Martina Hingis and Justine Henin as the only players to knock out the Williams sisters in consecutive rounds of a major.
Despite being top of the rankings, Halep does not feel like the superior player against seven-times Melbourne champion Serena.
“For sure she’s the best player in the world because she won so many Grand Slams,” Halep added.
“I cannot compare my results to her. But in this moment I am confident that I am in this position and I’m positive about it.”
Men’s top seed Novak Djokovic will continue his quest for a record seventh Australian Open title against 22-year-old Russian Daniil Medvedev, who has reached the last 16 of a Grand Slam for the first time.
Germany’s Alexander Zverev meets Canadian Milos Raonic in a battle of big hitters in the afternoon session on Rod Laver Arena.