The path from a top singles career to doubles specialist territory is a well-worn one. It's usually taken when a player gets older; their reflexes remain sharp, but the physical demands of singles are too much. In the current doubles Top 15, Hsieh Su-Wei and Vera Zvonareva both fit this trajectory.

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The reverse path is somewhat more unusual. Wimbledon champion Barbora Krejcikova is a rare example -- the Czech was a two-time doubles major winner before she cracked the singles Top 100. And this year has seen Japan's Ena Shibahara take the risk of putting her elite doubles career on the backburner in order to grind her way up the singles ladder from scratch.

"[At the start of 2024] I was like, 'I'm only getting older,'" No.217-ranked Shibahara said after defeating Daria Saville 6-3, 4-6, 7-6[6] in the US Open first round. "It's now or never."

As a junior, Shibahara, 26, boasted an excellent doubles record, winning the 2016 girls' doubles title alongside Jada Hart. But the UCLA alumna never planned to be a specialist in the discipline as a pro -- it's simply that the results came first. She cracked the doubles Top 100 in 2019, when her singles ranking still languished outside the Top 400.

By the end of that year, Shibahara had won her first two tour doubles titles alongside Shuko Aoyama. That partnership would go on to net her 10 trophies (including two at WTA 1000 level), one Grand Slam final at the 2023 Australian Open, qualification for the Tokyo Olympic Games in 2021 and a career high of No.4. Additionally, she joined forces with Wesley Koolhof to capture the 2022 Roland Garros mixed doubles title.

"It was hard to step away from that," Shibahara said. "There were a lot of reasons [I didn't focus on singles earlier] -- Covid was one of them. I had a higher doubles ranking, being on tour was great and I had an amazing doubles partner, and I also had a dream to well in doubles."

But Shibahara still missed the singles game -- so at the start of this year, with a ranking of No.581, committed herself to the toil of the ITF World Tour. She started in Nonthaburi, Thailand, where she reached the semifinals. She took herself to Spring, Texas -- where she claimed her first pro singles title -- and to Warmbad-Villach, Austria and Porto, Portugal. Along the way, Shibahara had to relearn how to play the game in a different way.

"[The biggest differences were] the physicality and the movement," she said. "Doubles is very fast, with a lot of footwork, but I have to have way better court coverage in singles. And also to have a very solid base. I know I have a lot of weapons, it's just how to use them."

Shibahara battles past Korpatsch, notches first WTA singles win of career

At the Prague WTA 250 in July, Shibahara fell in qualifying -- but got into the main draw as a lucky loser, then came through a 3-hour marathon against Tamara Korpatsch to win her first WTA match 7-6(5), 3-6, 7-5. That win was crucial, lifting her ranking to No.232 in the week of the US Open qualifying cutoff. Shibahara ended up being the last direct acceptance, fulfilling the aim she'd set for herself at the start of the year.

"My goal at the beginning of the season was to make Slam qualies," she said. "I was talking to so many people about how I was 10 out [of the US Open qualifying cut], then six out. Everyone was like, 'Oh my gosh, you're almost there.' Then literally a day before the draw was made, I got in. Last in. On the one hand, it was my goal. But on the other, it was ahead of schedule. I'm so glad I could embrace it and do as well as I'm doing."

Photos: Ena Shibahara and all of 2024's three-hour matches

Shibahara has certainly made stellar use of her Grand Slam qualifying debut. She battled through two three-setters, over Katarina Zavatska and Arianne Hartono, to reach the main draw, then won the longest match of the first round at 3 hours and 17 minutes over Saville -- a contest she describes as an "emotional rollercoaster."

Her reward -- beyond a singles ranking that will put her in a good position to contest Grand Slam qualifying in 2025 -- is the opportunity to test herself in one of the greatest challenges in the singles game as she takes on World No.1 Iga Swiatek in the second round. Shibahara has never played the Pole in singles but has won both of their doubles encounters. In 2016, Shibahara and Hart edged Swiatek and Kaja Juvan 6-3, 4-6, [10-4] in the US Open junior semifinals; in 2021, Shibahara and Aoyama defeated Swiatek and Bethanie Mattek-Sands 3-6, 7-6(4), [10-2] in the Miami semifinals.

Regardless of the outcome, Shibahara's run in New York means her gamble has paid off. She didn't see her singles experiment as a risk, knowing she would have doubles to fall back on if it didn't work out -- but also preferred to think positively.

"I thought, if it goes well for me in singles, then hopefully I can play both singles and doubles on tour," Shibahara said.

That outcome is within reach for her now.