CHARLESTON, SC, USA - Top seed Sloane Stephens tapped into her grit in the Round of 16 at the Volvo Car Open, engineering a propulsive comeback to defeat Ajla Tomljanovic, 4-6, 6-4, 6-4 in the Round of 16. 

Stephens found herself trying to fight out of a deficit in all three sets, coming back from a set and 0-3 to force a third set, and then again coming back from a break down at 3-4 to win the last three games of the match. A Charleston champion in 2016, the win put the American into her first quarterfinal of the season.

"For the first time in a long time I really was like, I gotta beat this girl," Stephens said after the match. "Like, I wanted to be out there, and I was really fighting, and I didn't care what it took. But you guys obviously see me play a lot, and I was like running to the baseline on the changeovers when I was down 3-0. 

"I was like, okay, I gotta figure out a way, and I definitely think my attitude is what won me the match today."

Asked why she wanted to win this match more than other recent matches, Stephens was nothing but honest.

"Because I was tired of losing! It sucks!"

Stephens arrived in Charleston with a 6-6 record through the early hardcourt swing, and had not beaten a Top 50 player since January. But the 26-year-old has consistently cited clay as her favorite surface, a proclamation that proved prescient last year, when she made her second major final at Roland Garros. Expectations were high for Stephens after her strong finish to the 2018 season, making the final of the WTA Finals in her tournament debut. So far, the clay has proven to be a salve. It's a surface that's provided more margin for Stephens to reign in her game. 

"It's just obviously a slow start to the season," Stephens said. "You gotta figure it out somewhere, and it eventually gets going, but you have to make it happen for yourself. Like I have to show energy and fight and try to turn it around for myself." 

WTA Insider Clay Court Power Index: Stephens slides in at No.7

"It's tricky for everyone, but on clay you have a lot of time. You have a lot of time to figure it out, and even like today when you're down 6-4, 3-0, it's never over because you can fight your way back and battle your way back and run around and try to figure it out. So I think that's what's pretty cool about clay."

Stephens' fight has been the story of her tournament in Charleston. In her opening round, the World No.8 needed over two-and-a-half hours to get a straight-set win over No.78 Sara Sorribes Tormo, grinding out a 7-6(4), 7-6(4) win. With her win over Tomljanovic, Stephens tallied back-to-back wins for the first time since making the Round of 16 at the Australian Open.

"Even if it doesn't help me out tomorrow, I won two matches in a row. Hello! I haven't done that since the Australian Open," Stephens said. 

READ: Sloane Stephens - 'I'm going through a transition, it's tough'

"So it's a good start. You gotta start somewhere. And obviously my attitude and being happy to be out there and wanting to compete and fight and having just a better outlook on it, I think, will help me just in general in the next couple of weeks or whatever. 

"And whatever happens tomorrow I'm going to go and do the same thing I did today, try to do my absolute best, and whatever happens, happens."

Stephens faces No.8 seed Madison Keys in the quarterfinals, a rematch of last year's Roland Garros semifinal.