Second seed Simona Halep followed the same express path into the second round of the US Open as Serena Williams, advancing 6-2 3-0 after Marina Erakovic retired with a knee injury.
The in-form Romanian, who reached the finals at US Open tune-up events in Toronto and Cincinnati, barely broke a sweat on a sunny Arthur Ashe Stadium court, needing a mere 47 minutes to see off the 99th-ranked New Zealander.
Top seed Williams, bidding to complete a calendar sweep of the four grand slams, advanced on Monday in similar fashion as she was up 6-0 2-0 when Russia's Vitalia Diatchenko was forced to retire hurt.
While the top two women's seeds steered clear of trouble, upsets continued up and down the women's draw for a second consecutive day as sixth seed and French Open finalist Lucie Safarova fell 6-4 6-1 to Ukrainian Lesia Tsurenko.
Safarova joins a number of first round casualties that already includes seventh seed Ana Ivanovic, eighth seed Karolina Pliskova and 10th seed Carla Suarez Navarro.
"I wasn't surprised (by the upsets), it is normal," said 23-year-old Halep. "Everyone is fighting like crazy because it's the last grand slam (of the year). When you play the grand slam you have just to give everything you have.
"I had this year already two grand slams where I lost in first and the second round."
Britain's Laura Robson threw away a 4-0 lead in the deciding set as she lost to Elena Vesnina.
Robson is still in the early stages of her comeback from an 18-month absence with a wrist injury and the 21-year-old looked on course for her first grand slam win in two years.
Vesnina, however, battled back from two breaks down in the third set to claim a 3-6 6-3 7-5 victory.
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