No.1 seed Serena Williams holds a 3-0 head-to-head lead across all three surfaces over compatriot Christina McHale - but none of those wins, all in 2016 as the World No.1, came easily. In the second round of Miami, Williams led 6-3, 5-3 and held a match point before McHale forced a third set, with Williams eventually winning 6-3, 5-7, 6-2 in two hours and eight minutes; in the third round of Rome, she needed to save a set point before pulling away 7-6(7), 6-1; and in the second round of Wimbledon, she would miss a set point in the first set and need to come from 0-2 down in the decider before triumphing 6-7(7), 6-2, 6-4 in two hours and 35 minutes. However, after surviving McHale, Williams would go on to lift both the Rome and Wimbledon trophies.
Coco Gauff could face Williams in a popcorn quarterfinal if both win their matches today. The 15-year-old Gauff will be taking on Laura Siegemund for the first time, and is bidding to reach the last eight of a WTA event for the second time following her Linz title in October. This week, Gauff is ranked at a career high of World No.67 while Siegemund is at World No.73, making this just the second time that the American teenager has faced a lower-ranked opponent in a WTA main draw (following her win over Stefanie Voegele in the first round of Linz).
2015 and 2018 runner-up Caroline Wozniacki takes on 2017 champion Lauren Davis for the third time today. No.5 seed Wozniacki is yet to drop a set to the American, having won 7-5, 6-1 in the 2017 Doha quarterfinals and 6-1, 6-3 in the first round of Beijing last year.
Two-time defending champion Julia Goerges is one of only three players to have won consecutive Auckland titles, along with 1988-89 champion Patty Fendick and 2003-04 winner Eleni Daniilidou. The German will bid for her sixth consecutive quarterfinal today in her first meeting with Prague and Palermo champion Jil Teichmann.
ORDER OF PLAY
STADIUM (starts 12 noon)
Coco GAUFF (USA) vs Laura SIEGEMUND (GER)
 Serena WILLIAMS (USA) vs Christina MCHALE (USA)
Not before 3.30pm
Jil TEICHMANN (SUI) vs  Julia GOERGES (GER)
Not before 7pm
 Caroline WOZNIACKI (DEN) vs Lauren DAVIS (USA)
Caroline GARCIA (FRA) / Julia GOERGES (GER) vs Asia MUHAMMAD (USA) / Taylor TOWNSEND (USA)
GRANDSTAND (not before 4.30pm)
 Desirae KRAWCZYK (USA) / Laura SIEGEMUND (GER) vs Kirsten FLIPKENS (BEL) / Alison VAN UYTVANCK (BEL)