Amelie Mauresmo recovered from a third set deficit to defeat compatriot Julie Coin 5-7 6-2 7-6 at the Brisbane International.
The former world number one needed over three hours to beat Coin, saving match points in the process.
"I felt it was long, so long. It's tough. I'm tight everywhere. A lot of work for my physio," Mauresmo said.
The 2006 Australian Open and Wimbledon champion had her service broken four times and produced 10 double-faults during the course of the match.
She added: "Too many mistakes, too many missed chances, yeah, it was a strange one.
"I really don't know what to say about this match. I'm just glad I won it because it would have really been the 'missed-occasions match' if I didn't. That's the good and positive point for today."
Mauresmo will play either top seed Ana Ivanovic in the quarter-finals after the Serbian beat Italy's Roberta Vinci 6-7 (4-7) 7-5 6-1.
French success continued in the men's draw at Brisbane.
Ernests Gulbis was beaten by Paul-Henri Mathieu a day after Gulbis had upset top seed Novak Djokovic.
Two other Frenchman, Jo-Wilfried Tsonga and Florent Serra, joined Mathieu in the last eight.
Third-seeded Spaniard Fernando Verdasco also progressed with a 6-2 6-3 victory over Mario Ancic.

Federer overjoyed with Verdasco win
World Tour Finals - Day One
Winning start for Murray at O2
Murray v Del Potro
London calling Murray
ATP World Tour Finals Preview
Djokovic feeling confident
Fleming - ATP had vested interest
We take a closer look at the ATP World Tour Finals and give our verdict on the likely finalists in London.
Novak Djokovic is convinced his hard work will pay off during his World Tour Finals defence.
While Pac Man may have won big in Vegas, others in the world of sport didn't fair so well at the weekend.