CINCINNATI, OH, USA -- Kiki Bertens of the Netherlands picked up another upset during her breakout 2018, moving past No.5 seed Elina Svitolina of Ukraine, 6-4, 6-3, to reach the semifinals at the Western & Southern Open on Friday.

"I never did so well in the hard court season, over the last few years I didn't win many matches, so it was just like coming here, trying to play as many matches as I could," Bertens told the press, after her victory. "Last week I had a few, and now I'm even doing better. So I'm really happy that I can play so many matches."

Bertens has claimed six Top 10 wins since Wimbledon, including two last week at the Rogers Cup, as her ascendancy into the WTA elite continues with her 84-minute victory over Svitolina, which featured a first-set comeback from 1-4 down.

"We were trying already in the beginning of the year to play a little bit more aggressive, to go a little bit more for my shots sometimes," Bertens said, regarding her improvement. "And I think also the movement is much better. I'm much fitter and I can reach more balls, so I think that's also helping a lot. So I think it's a combination of a lot of things."

Bertens will face No.8 seed Petra Kvitova in the final four, after the Czech lefty squeaked past Elise Mertens of Belgium in an earlier quarterfinal. They have played twice this year, with Kvitova triumphing in the Mutua Madrid Open championship match before Bertens exacted revenge last week at the Rogers Cup.

"Last week [against Kvitova] was pretty tough, like, tough circumstances with the wind, which she doesn't really like," Bertens explained. "So I was just playing as many balls in the court there. I was serving good, and tomorrow I have to do the same. So just focus on the serve, trying to hit as many balls in the court with a lot of quality. So, yeah, it's not going to be easy."

Svitolina started the match on a mission, taking advantage of an error-prone Bertens to clinch the initial break at 3-1 in the first set. The Ukrainian consolidated her break for a 4-1 lead as she seemed to take control of the opening frame.

But the Dutchwoman's powerful serving kept her in good stead throughout the match, and after holding for 4-2 with an ace, Bertens got back on serve in the next game to reach 4-3. Then, after leveling the set at 4-4, Bertens notched another break of service, charging to the net to put away a forehand winner and give herself a chance to serve out the opener.

After one set point fell by the wayside, Bertens garnered a second with a winning backhand volley, and after Svitolina fired a backhand return long, the unseeded player stood with a one-set advantage after reeling off five games in a row. Bertens nearly tripled Svitolina's amount of winners, with the Dutch player leading that metric by 13 to five.

Unlike the first set, Bertens took the initial lead in the second set, as the Dutch World No.17 pulled off a stunning break of service at 2-2, deploying a drop shot to reach her third break point of the game, and getting the conversion with a forehand winner.

Bertens broke Svitolina again, giving her the chance to close out the match on her serve at 5-2, and the Dutchwoman reached match point. But Svitolina hung tough, eventually reaching break point after a double fault, and taking the game to extend the match.

However, Bertens rebounded in the following game, and, at 30-30, slammed a service return deep into the court to force a netted error by Svitolina a claim a second match point. On this chance, Bertens nailed a perfect backhand drop volley to secure the victory and keep another strong week going.