MELBOURNE, Jan 20 (Reuters) - World number one Ash Barty and defending champion Naomi Osaka could set up a tantalising fourth-round showdown at the Australian Open with victories at Melbourne Park on Friday. Barty, whose stunning form has seen her drop just three games so far, takes on 30th seed Camila Giorgi in the third round, while Osaka faces Amanda Anisimova, who won the Melbourne Summer Set 2 tournament in the lead-up. Barty and Osaka have both won twice against each other but have not met in over two years. In a battle of the French Open champions, holder Barbora Krejcikova plays 2017 winner Jelena Ostapenko, while Victoria Azarenka continues her quest for an unlikely third Australian Open title against 15th seed Elina Svitolina. Among the men, the up-and-coming Carlos Alcaraz will be in action against seventh seed Matteo Berrettini on Rod Laver Arena, which will be followed by another heavyweight clash involving 20-times major winner Rafa Nadal and the big-hitting Karen Khachanov. World number three Alexander Zverev is also in action on Friday following his straight-sets demolition of Aussie John Millman, with the German hoping to stay on course for a maiden Grand Slam triumph against qualifier Radu Albot.