Before arriving in New York last month for US Open qualifying, Janice Tjen had won 45 of her last 50 professional matches.

During that stretch, she reached nine ITF finals, winning six, and climbed more than 200 spots in the rankings — from No. 371 to No. 149.

São Paulo: Scores | Draws | Order of play

But even after bursting onto the scene with a first-round win over Veronika Kudermetova in her Grand Slam and WTA debut, questions lingered about how she’d adapt to life on the main tour.

Those questions have now been answered.

Tjen defeated Francesca Jones 7-6 (0), 6-3 in 1 hour and 32 minutes Saturday in São Paulo to reach her first WTA final.

“It’s special,” Tjen said after the match. “It’s my first WTA tournament outside of a Grand Slam, and being able to reach the final is a bonus. But at the end of the day, it’s just another match so I’ll see how I do tomorrow.”

With the win, the 23-year-old became only the third Indonesian to reach a WTA final in the Open era, following in the footsteps of Yayuk Basuki and Angelique Widjaja.

It also marked Tjen’s 63rd victory of the season — and her 58th on hard courts.

A key to the win? Her much-improved serve. Tjen finished with eight aces, which she credited to the work she’s been putting in behind the scenes.

“Me and my coach have been working on my serve almost every day,” Tjen said. “And it’s nice to see it paying off little by little.”

In addition to the uptick in aces, Tjen won roughly 90% of points on her first serve and was an even more impressive 71% on second-serve points.

While those numbers may be tough to replicate in Sunday’s final, she’ll aim to match them when she faces Tiantsoa Rakotomanga Rajaonah for the title.

They have yet to face each other in their careers.

Rakotomanga Rajaonah shows hard-court mettle

Known for her prowess on clay, French phenom Tiantsoa Rakotomanga Rajaonah is proving she’s more than a clay court specialist.

The 19-year-old defeated Renata Zarazua 6-3, 6-2 in 1 hour and 20 minutes Saturday on Quadra Central Maria Esther Bueno to advance to her first WTA final.

Her victory — her third over a Mexican opponent this week — guarantees a first-time WTA title winner in São Paulo.

“I try to be really aggressive while also being really focused on what I’m doing,” Rakotomanga Rajaonah said after the match. “No pressure, just go for it.”

She practiced what she preached, playing fearlessly from the start. She ripped 29 winners to Zarazua’s four and, after breaking for a 3-2 lead in the first set, never gave Zarazua any real hope of getting back in the match.

She’ll need that same approach against Tjen.

Regardless of the result, it’s been a breakthrough week for the Frenchwoman, who entered the tournament with a WTA 250 quarterfinal and a W100 final on her résumé — but little hard-court success this season.

In fact, if Rakotomanga Rajaonah wins Sunday, it will be her first career title on a hard court at any professional level.