CINCINNATI, OH, USA - Unseeded Sofia Kenin beat Elina Svitolina in straight sets for the second straight week on Thursday night to advance to the quarterfinals of the Western & Southern Open, 6-3, 7-6(3).

After failing to convert a match point as she double faulted serving for the match at 6-3, 5-4, but managed to hold off the Ukrainian in a tight two-setter to continue her sizzling summer form.

"I didn't close it out the first time, which was obviously tough, but I'm just so happy to have played through and fought through. She's such a tough player...and this is really special," Kenin said.

"Having these really tough matches, playing well, I'm really happy with how I'm playing on court and proud of myself.

"I'm really pleased. This was honestly high quality tennis. Elina is such a tough player and we both literally gave everything on court. We had these really tough, long rallies and she's such a tough player and a great competitor."

The American also beat Svitolina in the quarterfinals of the Rogers Cup last week, which followed her second round victory over then-World No.1 Ashleigh Barty, the first such win of her career.

Both players had ample chances to break in the early stages of the match, as they faced six combined break points across the first three games.

Kenin steadied with a love hold to lead 3-2, and scored the deciding break of the opener in the sixth game to move ahead from then on.

The 20-year-old was again the first to break in the second set, as she won Svitolina's serve for a second time to lead 3-2, but after surrendering serve herself for the first time, the American again broke the No.7 seed to serve for the match.

"When I double faulted, which was really upsetting, I just tried to tell myself to keep fighting and not give up," Kenin said about seeing her first match point slip away.

"When the tiebreak started,  I felt like I needed to get a good lead, and I felt pretty comfortable in the tiebreak because I beat her in a tiebreak in the first set last week.

"I was getting confidence as I went, and at 5-1, or something, I said, 'Now I finally have a chance to win!' and I'm happy I closed it out."

In order to reach the semifinals in Cincinnati, Kenin will have to dethrone another, as she takes on reigning Australian Open champion Naomi Osaka in the last eight.

"She's a tough player and having really great year," Kenin said. It's going to be a great match and we'll see how it goes. I'm just going to rest up, because I need it.

"She's got a big serve, big shots. She obviously plays differently [than Svitolina] so it's going to be a good matchup. I'm excited for tomorrow and I'm just looking forward to compete."