US Open champion Coco Gauff brushed aside Brenda Fruhvirtova 6-3 6-0 at the Auckland Classic on Thursday.
However, Emma Raducanu, making a comeback following an eight-month injury layoff, was not able to qualify for the last eight after the former Flushing Meadows champion went down 6-7(5) 7-6(3) 6-1 to second seed Elina Svitolina.
Fruhvirtova, 16, fought well during the start of the match but once the American didn’t look back after taking a 3-2 lead.
Gauff quickly claimed a 5-0 lead in the second set but the 19-year-old was forced to save two break points before winning her first career clash with the Czech.
"(Fruhvirtova) started off playing really well, and I was able to raise my level," Gauff said. "I thought I served well and did better on the returns, and I think I played a great match today."
On the other hand, Raducanu won the first set of her match and also took a 3-1 lead in the second set tie-break before Svitolina staged a comeback to run away with the match.
"It was really a great match from both of us. I think Emma played a great match as well," Svitolina said.
"It was really difficult physically, I just hope I will recover for tomorrow."
Meanwhile, at the Brisbane International, former French Open champion Jelena Ostapenko defeated Karolina Pliskova 6-2 4-6 6-3 to qualify for the quarters.
Latvian Ostapenko, who will meet former world number one Victoria Azarenka in the next round, easily won the first set but was left frustrated as Pliskova didn’t give up and claimed the second.
"I get really mad when I miss some important points and I get really angry at myself," Ostapenko said.
"I'm a fighter and I really want to play kind of perfect. But I know nothing is always perfect. It’s just the way I am."
Two-time champion Azarenka claimed a win against France's Clara Burel 7-5 6-2.