"Super-focused" world number one Aryna Sabalenka hit 23 winners as she beat Jaqueline Cristian to move into the fourth round at Indian Wells.
The Belarusian, 27, had been on track to take the opening set but double faulted as she looked to serve it out.
A swift break back allowed the four-time Grand Slam champion to take it 6-4, though, and she followed that by winning the second set 6-1 to seal victory.
"I knew that she was not going to give up easily," Sabalenka said of Romanian Cristian, the world number 35.
"That's why I was super-focused, especially on my serve.