Karolina Pliskova is aiming to qualify for the WTA Finals in Singapore following her run at the U.S. Open, her coach said.

Pliskova won the title in Cincinnati and defeated both Venus and Serena Williams to reach the final of the U.S. Open. She had not previously reached the second week of a major.

"She [improved] her game, and she [believes] in herself now," Jiri Vanek, her coach and a former ATP player, told TENNIS.com. "[That] is important for that kind of player."

Vanek was not particularly surprised by Pliskova's sensational performance in New York.

"I knew Karolina is a great player,” he said. "[It was] just her attitude on the court. [She] was not believing in herself."

The 24-year-old first broke into the Top 10 a year ago, but Vanek said that her ranking and confidence dropped as other players started raising their games against her. That led the pair to look for changes following the French Open.

"I said, ‘Just be normal, just focus on yourself. We have to start something new,’” he said. "We started working with new fitness coaches. They improve so much—her movement, and she's more stable now, more bending her knees … because she has very long legs. And so I think she also [improved physically].”

She will now look to build on her new-and-improved game, as well as her successful summer.

"I hope she's going to stabilize this type of game," he said. "I hope she can make the Finals in Singapore, and we will concentrate on that."

Pliskova is No. 6 in the rankings.