Australian Open Day 6 matches to watch: Americans take center stage
Venus Williams attempts to make the fourth round of a Slam for the first time since 2011
While no official reason was given for Venus and Serena's withdrawal from doubles, it's possible the decision is a signal of Venus' confidence in her singles chances in Melbourne. She is undefeated to start the year and has lost just one set in seven matches this season. She plays the hard-hitting Camila Giorgi in the first match on Margaret Court Arena. This is their first meeting.
Madison Keys and Varvara Lepchenko go for big upsets
Both Americans have an opportunity at a big scalp on Saturday and they bookend the action on Rod Laver Arena. No. 30 Lepchenko will go for her third consecutive win over No. 6 Agnieszka Radwanska (first match, Rod Laver Arena). Lepchenko beat her twice last year on hard courts. Keys has the tougher task later in the evening when she plays No. 4 Petra Kvitova (second night match, Rod Laver Arena). Kvitova won their only meeting, a 6-2, 6-2 win in 2013.
"I think there'll be lots of long rallies," Keys joked. "I think it's just one of those matches where we're both fighting to be the aggressor first. I think that will be the entire match. I think whoever wins will be whoever was able to do that consistently and the best."
Serena Williams gets a test from No. 26 Elina Svitolina
Svitolina can play. The 20-year-old from Ukraine is a great competitor with a powerful game off the baseline. She already has a Top 10 win this season, having beaten Angelique Kerber to make the Brisbane International semifinals. Serena can't afford any lapses. They'll play in the second match on Rod Laver Arena.
More matches to watch
Novak Djokovic  vs. Fernando Verdasco  (7 p.m. local time/3 a.m. ET, Rod Laver Arena): Djokovic lost just five games in his last match and he's looked incredibly sharp, as he usually does at Melbourne Park.
Kei Nishikori  vs. Steve Johnson (5 p.m. local time, 1 a.m. ET, Hisense Arena): Johnson hasn't taken a set off Nishikori in two matches but he's always played him tough. Could be interesting.
CoCo Vandeweghe vs. Madison Brengle (third match, Hisense Arena): This is a massive opportunity for each of these young Americans to book a spot in the fourth round of a Slam for the first time. This is their first meeting on the tour-level. Vandeweghe won two of their three matches down in the ITFs.
Dominika Cibulkova  vs. Alize Cornet  (12:30 p.m. local time, Show Court 2): Come for the drama. Stay for the...drama.
John Isner  vs. Gilles Muller (6 p.m. local time, 2 a.m. ET, Show Court 3): Isner hasn't advanced to the fourth round of a hard court major since the 2011 U.S. Open. He's 3-0 against Muller.
Garbine Muguruza  vs. Timea Bacsinszky (first match, Hisense Arena): Few women are playing as above their rank as Switzerland's Bacsinszky. Currently ranked No. 41, she's beaten Sharapova and Kvitova in the last five months and beat No. 15 Jelena Jankovic in the first round in Melbourne. The winner of this match could play Serena in the next round.