TOKYO (Kyodo) -- Having made a name for herself as a doubles specialist, Ena Shibahara has shown she also has what it takes to stand out in singles, according to Japan's Billie Jean King Cup captain Ai Sugiyama.

Shibahara filled the singles spot vacated by injured former world No. 1 Naomi Osaka at the team event's finals last month in Spain, winning both of her matches against higher-ranked opponents in Japan's 2-1 first-round win over Romania and 2-1 quarterfinal loss to eventual champion Italy.

"She has the potential to break in the top 20 in singles," Sugiyama said of the 26-year-old. "She listens to me and teammates in any situation during matches without panicking."

Shibahara entered the event ranked 135th in the world as Japan reached the 12-team cup finals for the first time since the current format was introduced in 2020.

The 2022 French Open mixed doubles champion with Wesley Koolhof of the Netherlands, Shibahara defeated then No. 73 Jaqueline Cristian of Romania 6-4, 7-6(2) on Nov. 14.

Two days later, she rallied to beat then No. 54 Elisabetta Cocciaretto of Italy 3-6, 6-4, 6-4.

After calmly listening to Sugiyama during a changeover, Shibahara managed to improve her footwork and turned the match around against Cocciaretto.

"This is definitely a confidence boost," Shibahara said of her two wins.

Shibahara, who grew up in the United States, serves at over 180 kilometers (112 miles) per hour. She played in women's and mixed doubles events at both the Tokyo and Paris Olympics and now plans to shift her focus to singles.

But the 11-time women's doubles tournament winner on the WTA Tour is aware that things will not be easy against great players from around the world.

"I still have a lot to work on," Shibahara said.