Brisbane - French Open champion Garbine Muguruza saved a match point before seeing off Russia's Daria Kasatkina in the second round of the Brisbane International on Tuesday.
The 23-year-old Spaniard won 7-5, 3-6, 7-6 (9/7) over the 19-year-old Kasatkina, who served for the match at 5-4 in the third set, only to be broken by the fourth-seeded Muguruza.
Muguruza then kept her nerve in the tiebreak, holding on to win in just under three hours.
It was her second three-set win in as many days after she edged Australian Samantha Stosur on Monday.
Third seed Czech Karolina Pliskova earlier continued her impressive form when she stormed past US qualifier Asia Muhammad 6-1, 6-4.
However, sixth seed Elina Svitolina was pushed hard by American Shelby Rogers before winning in three sets 7-5, 2-6, 7-5.
Frenchwoman Alize Cornet stormed into the quarter-finals when she demolished Christina McHale in straight sets 6-2, 6-1.
After outlasting Elene Vesnina in the first round in a two hour, 37 minute marathon in temperatures above 40 degrees Celsius (104 F), Cornet took full advantage of the much cooler conditions Tuesday and raced through the match in just 81 minutes.
"I'm very happy with the way I played today -- it was a really good-quality match," Cornet said.
"I didn't make a lot of unforced errors and I hit a lot of winners.
"I was applying the right tactics, so it was great to play this way."
Cornet will play either second seed Dominika Cibulkova or China's Zhang Shuai in the quarter-finals.
"It will definitely be a tough battle but when I see the way I play today it gives me a lot of confidence for the rest of the tournament."
Earlier, Australian teenager Destanee Aiava created a slice of history when she became the first player born in the 2000s to win a main draw match on the WTA Tour.
The 16-year-old Aiava beat fellow qualifier Bethanie Mattek-Sands of the US 2-6, 6-3, 6-4 in a rain-delayed first-round match.