“Sports games are not usually comfortable spaces for trans people,” Ms. Bueno added. “She is doing so much for us, so we want to do something for her, too.”

Volleyball is the second-most popular sport in Brazil, after soccer, and millions tune in for big games.

Ms. Abreu, 33, is the first transgender volleyball player to make it to Brazil’s top ranks. If she qualifies for the 2020 Olympics in Tokyo — which experts say is probable — she would be making history as one of the first openly transgender athletes to participate in the Games.

Photo

The 2020 Games are expected to be the first in which openly transgender athletes will compete, even though guidelines establishing eligibility based on hormone levels have been in place since early 2016.

Brazil is a powerhouse when it comes to volleyball and the women’s national team has twice won Olympic gold, in 2008 and 2012.

“Just like any other player, I’d like to go to the Olympics,” Ms. Abreu said in a postgame interview after greeting fans. “But I know it’s not going to happen just because I’m getting all this attention. I’ve got to do my best as a player.”

Ms. Abreu says she is trying to limit her media exposure after her success gave rise to widespread debate about whether male-to-female transitions give athletes an unfair advantage — an argument that has been going on at least since Renée Richards, a transgender woman professional tennis player, competed in the U.S. Open in 1977.

Advertisement Continue reading the main story

After joining the women’s professional league last year, Ms. Abreu’s performance on the court quickly caught the nation’s attention. In less than a month, she was scoring the highest number of points a game on average. And in January, she beat the record set by one of Brazil’s Olympic stars, Tandara Caixeta, for total points scored in a single game: 39 (a record Ms. Caixeta has since matched).

Ms. Caixeta has helped fuel the debate about any edge transgender athletes may have.

“I really respect her and her history,” Ms. Caixeta said in an interview given to sports journalists after her record was broken. “But I don’t agree with her participating in the feminine Superliga. It’s a very delicate issue and it’s not homophobia. It’s physiological.”

Ms. Abreu began playing volleyball at the age of 17 and eventually made it to the men’s professional leagues in Europe. Toward the end of her time there, she adopted the name Tifanny.

In 2012 she decided to begin her transition to a woman, even if it meant giving up volleyball.

“I knew I was a girl since I was a child,” she said. “I love volleyball, but it is just my job. The day I’m no longer working, I’ll still be happy because I am me, Tifanny, the person I always imagined.”

Before leaving Europe, she underwent sex reassignment surgery, changed her name on all official documents and began hormone replacement treatment.

Photo

As her transition was starting, a long-running debate in the sports world about athletes like Ms. Abreu began to shift in her favor.

In January 2016, the International Olympic Committee decided to allow transgender men and women to compete without undergoing sex reassignment surgery. Athletes who have transitioned from female to male may boost their testosterone levels but must undergo tests and submit reports to avoid being accused of using a performance-enhancing drug.

Male-to-female transgender athletes are required to reduce the testosterone in their blood to below 10 nanomoles per liter. Typical values for women are 0.5 to 3.0 nanomoles per liter.

Newsletter Sign Up Continue reading the main story Please verify you're not a robot by clicking the box. Invalid email address. Please re-enter. You must select a newsletter to subscribe to. Sign Up You agree to receive occasional updates and special offers for The New York Times's products and services. Thank you for subscribing. An error has occurred. Please try again later. View all New York Times newsletters.

Ms. Abreu lowered her levels to 0.2 nanomoles. In 2017, the International Volleyball Federation and the Brazilian Volleyball Confederation authorized her to play on women’s teams, and in December she started playing for her team in Bauru, a conservative agricultural hub.

Advertisement Continue reading the main story

Ms. Abreu, who at 6-foot 3-inches is tied for the tallest member of her team, has said herself that a transgender woman might have some advantages in volleyball, but she points out she is complying with all of the rules. Her teammates have spoken out in support.

“She’s tall and strong, but nothing out of the ordinary for a spiker. She also makes mistakes,” said Angélica Malinverno, Vôlei Bauru’s captain.

“Most of us aren’t from here,” Ms. Malinverno added, referring to Bauru. “So we end up becoming one big family. Tifanny was accepted from the beginning. She’s funny and likes to joke around.”

The debate about advantages will likely grow ahead of the 2020 Games amid anticipation that at least two openly transgender athletes could participate. The other probable athlete is Laurel Hubbard, a New Zealand weight lifter.

“It will be a historic moment,” said Joanna Harper, a medical physicist and transgender athlete who advised the I.O.C. on the new guidelines. “This area is very controversial, and you will get a number of opinions.”

Photo

Ms. Harper, who published a study on transgender athletes, says transgender women who go through puberty as males do have advantages that cannot be eliminated completely through hormone therapy.

“It reduces muscle mass, but not to typical female averages,” she said. “On average, transgender women are taller, bigger and stronger. For many sports, including volleyball, these are advantages.”

But, she added, they also have disadvantages. The main one is they maintain their typically larger frames, but with reduced muscle mass and aerobic capacity.

Advertisement Continue reading the main story

After studying hours of Ms. Abreu’s games, Ms. Harper said that factor explains why the Brazilian star is such a formidable spiker but slow, and even a bit of a liability, in the back of the court. She noted that since Ms. Abreu joined Vôlei Bauru, the team has inched up just one place in the Superliga ranking, to eighth.

Nonetheless, she said it wouldn’t be “unreasonable” for high-level volleyball organizations to be more restrictive. “They could put in a rule limiting each team to one transgender player,” she said.

The use of quotas has been defended by Ms. Abreu, who noted there were already quotas for the highest-ranked players and for foreign players.

But her fans at the recent game were outraged by the idea. “That would be institutionalizing homophobia,” said Carue Contreiras, an activist for gay and transgender rights from São Paulo. “How would that be different from the quotas they once used to limit the participation of black athletes?”

For Hairton Cabral, the coach of the rival team from São Caetano do Sul, the solution is more studies on the performance of transgender athletes. “For coaches, it doesn’t matter as long as it’s legal — we just want the best performers. But the whole issue is very politicized, and the only way to stop that is with facts.”

Ms. Abreu’s team ended up losing the game. But she was the top scorer of the night, with 22 points, and the only player with fans from both teams waiting in long lines to snap a selfie with her.

“I am so proud to be able to be a model for them so they can grow up and play sports, too,” she said. “The little girls who are inspired by me and also the young transsexuals.”