Hong Kong - Last year's Hong Kong Open runner-up Daria Gavrilova admitted she had lost her concentration Thursday as she made hard work of dispatching unseeded Monica Niculescu over almost three gruelling hours.
The Australian needed a third set tiebreaker -- which she closed out with an emphatic smash -- to finally break her resilient Romanian opponent, whose forehand slice and confident net play unnerved the seventh seed.
Gavrilova started the match in cruise control but her game started to unravel towards the end of the first set as unforced errors crept in, and Niculescu fought back with an armoury that also included a powerful double-handed backhand.
"I probably was getting a bit too emotional and frustrated because I felt like I was dictating, but I was making too many errors," Gavrilova said.
"I stepped up my game but I wasn't really happy with the way I was going from super good to not great."
The 24-year-old described Niculescu as a "fighter" but added she had not made it easy for herself as she ground out the 6-3, 4-6, 7-6 (7/3) win.
"I was losing concentration -- I was really more mentally tired than physically and that is probably where the errors came from."
Gavrilova, the world number 34, has enjoyed an impressive run of recent form in Asia, beating world number 18 Jelena Ostapenko in Wuhan and stunning world number seven Petra Kvitova in Beijing.
But after two three-set matches so far this week, she now faces China's number two Zhang Shuai, who wrapped up a 6-1, 6-7 (4/7), 6-1 victory against the Netherlands' Lesley Kerkhove.
Speaking after the win, Zhang said she felt "everything is coming together".
She added: "I like playing Asia, I like playing China, Hong Kong -- I'm feeling happy here."
China's leading woman, Wang Qiang, needed only two sets to get past American Christina McHale 7-5, 6-1.
"I think I played really well tonight, so I have nothing to lose tomorrow," the sixth seed said ahead of her quarter-final.
Now ranked 24, Wang is chasing more WTA titles to go with the two she picked up in July and September in Nanchang and Guangzhou.
She added: "I think next year the target is top 20."