Last week, a historic NBA strike dominated the headlines. The Milwaukee Bucks’ decision to sit a game out spread across the league and then to the Women’s NBA, Major League Soccer, and even, remarkably, Major League Baseball and the National Hockey League. The Bucks took action in response to the shooting of Jacob Blake by police in Kenosha, Wisconsin, and the ongoing murder and brutalization of black people by the police in the United States.

While NBA players have since returned to work — after contentious negotiations, and with a nudge from Barack Obama — there is another labor story in the world of professional sports: some of tennis’s top male stars are pushing to form a players’ association, separate from the existing structure of the Association of Tennis Professionals (ATP), which jointly represents players and tournaments. But there are serious questions as to how much support the new association has, and what its purpose would be.

As reported by the Associated Press, “No. 1-ranked Novak Djokovic and former top-30 member Vasek Pospisil would be the co-presidents of a new group they are trying to set up to represent men’s professional tennis players.” A letter obtained by AP on Friday, sent to players before the start of this week’s US Open, seeks the creation of a Professional Tennis Players Association (PTPA).

Its objective, the letter says, is “to solicit support from players to form an association with a mandate to promote, protect and represent the interests of its players … and protect the future of tennis.” The effort seeks to represent men’s singles players in the top 500 and doubles players in the top 200, and would look into “ATP and tournament rules and regulations, revenue sharing, disciplinary actions, pensions, travel, on-site food and amenities, insurance and medical care,” according to the leaked email.

Unlike team sports in North America, tennis players do not have a union. Professional players are classified as independent contractors, not employees, and pay ranges widely among professional players. As Louisa Thomas recently wrote in the New Yorker, “In many respects, professional tennis doesn’t resemble something like the N.B.A. so much as it resembles a federation of, say, fifty or so states with separate governments and a reigning ethos of individualism.”

The men’s tour is put on by the ATP, while the Women’s Tennis Association (WTA) organizes the women’s tour — the two are entirely separate. Although the ATP and WTA have Player Councils, which give athletes a say in the sport, these are not a union, i.e., a representative body with the power to collectively bargain.

In a recent statement, Pospisil said the PTPA would have “essentially the same function as a union.” It is unclear whether that function includes the power to collectively bargain. As noted by ESPN, US labor law considers the tennis tour a monopoly, and thus players are barred from unionizing based on the argument that it would concentrate too much power in their hands.

As reported in the New York Times, on Saturday “both the men’s and women’s tours, along with the four Grand Slam tournaments and the International Tennis Federation, released a joint statement backing the ATP and supporting ‘its role in representing the best interests of players throughout this process.’” Said ATP chairman Andrea Gaudenzi, “You have what other athletes in other sports would strive for — a seat at the boardroom table.”

A letter penned by PTPA skeptics and obtained by the New York Times asks several questions of its proponents, such as “What happens if tournaments go against us?”; “What is the contingency plan to protect us if this goes ahead and badly?”; “Who is taking responsibility for any fallout both with our careers, income and negativity?”

At a time when the men’s and women’s players have expressed greater interest in working together, the decision not to include women in the PTPA has prompted questions as to whether the effort would only increase divisions across the sport. Djokovic’s leading role in the organizing exacerbates these suspicions: in 2016, the star said the WTA “rides on the coattails” of the men, and argued men’s tennis should get more prize money than women’s, because “we have much more spectators” than the women do.

Djokovic, Pospisil, and John Isner, the sport’s highest-ranked American man, all reportedly resigned their positions in the ATP in the past few days. Before his resignation, Djokovic was president of the ATP Player Council.

Roger Federer and Rafael Nadal, two of the tennis world’s biggest superstars, have come out in opposition to the effort, as has former US Open champion Andy Murray. In a recent comment on the PTPA, Murray said that while he’s not against a player union in principle, “the fact that the women aren’t part of it” gave him particular pause.

The PTPA’s success depends on whether its advocates, particularly Djokovic and Pospisil, can convince their fellow athletes that a players’ association will provide leverage that they lack within the ATP and WTA — of course, this presumes PTPA proponents will be pushed to bring women’s tennis players into the effort.

It’s true that workers need a body separate from management, but that is an argument that requires patient organizing: conversation after conversation with those whose input and energy is a prerequisite for such a body. Building a union, or even a nonunion “association,” is no easy task, and it can never work if proponents don’t win the majority to their position.