American Danielle Collins thrashed fourth seed and former champion Elina Svitolina in the first round of the Brisbane International on Monday as Angelique Kerber also crashed out. Svitolina, the world number five, went into the match as firm favourite but was never in the hunt against Collins, going down meekly 6-1, 6-1 in just 56 minutes.
She joins two other US players in the second round following wins by Sophia Kenin and Alison Riske.
Kenin beat Latvia’s Anastasija Sevastova 7-6 (7/1), 6-4 while Riske downed Czech player Karolina Muchova 6-4, 6-2.
In a battle of former Grand Slam champions, Australia’s Samantha Stosur upset former German world number one Kerber in two tough sets.
In other matches, Barbora Strycova upset seventh seeded Johanna Konta 6-2, 3-6, 6-3, and Ajla Tomljanovic beat Priscilla Hon 6-2, 4-6, 6-4.