Fifty years after the Women’s Tennis Association was founded on the basic principle of equality, some inequities persist.

On Tuesday -- on the eve of International Women’s Day -- a compelling argument came from an unlikely source: a player from the ATP Tour. In a compelling piece featured in The Players’ Tribune, Denis Shapovalov broke it down in stark but relatable terms.

After his girlfriend, Mirjam Bjorklund, qualified for a WTA Tour 250 event last year, Shapovalov was ecstatic.

“Oh, great,” he told her, “you’ll get at least $7,000 just to be in the main draw.

Bjorklund shot him a look he’ll never forget.

“Denis,” she said, “I think it’s like a thousand dollars.”

Shapovalov was incredulous. “What are you talking about?” he asked. “How is that possible?”

This past Sunday, Marta Kostyuk received $34,228 for winning the ATX Open in Austin, Texas, a WTA 250 event. On the same day in Santiago, Nicolas Jarry won the Movistar Chile Open. Like Kostyuk, he won five best-of-three matches, but Jarry collected $97,760 for his week’s work.

“I thought it was really amazing how [Shapovalov] took his chance to talk and that’s the subject he chose,” said Jessica Pegula, the Hologic WTA Tour’s No.3-ranked player, at the BNP Paribas Open. “It’s something that the men, I think for the most part, have supported. But it’s always if they get asked, they support it.

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“For him to go so out of his way to make that the main story he was talking to the press about was really cool. And really nice. I know all the women appreciated that a lot.”

One example cited by Shapovalov was last summer’s Citi Open in Washington, D.C., when Liudmila Samsonova took home $33,200 for winning the title.

“I made the final of the ATP 250 in Seoul last September,” Shapovalov wrote. “As a runner-up, I got $100,000. I mean, it’s not even close!

“I’m not sure everyone realizes how damaging this is for tennis. Unfortunately, it seems that if you are a female player, your chances of surviving as a pro are a lot lower … because you are a woman.”

Because Iga Swiatek had such a phenomenal season, winning eight titles, her season-ending prize-money total was $9.9 million – almost identical to the $10.1 million that went to the ATP’s leading money winner, Carlos Alcaraz. But going down the list, the difference becomes more glaring:

ATP No.10 Hubert Hurkacz ($3.8 million) versus WTA No.10 Simona Halep ($2.3 million), ATP No.50 Sebastian Korda ($1.1 million) versus WTA No.50 Aliaksandra Sasnovich ($794,000) and ATP No.100 Alexei Popyrin ($610,000) versus WTA No.100 Dayana Yastremska ($488,000). Percentage-wise, those margins are significant.

Ons Jabeur is well aware of the inequities in women’s tennis. In January, she was announced as a member of the Professional Tennis Players Association’s inaugural Player Executive Committee.

“We’re trying to get the right for all players equally but, yes, women need to have more and more rights,” Jabeur said Wednesday. “In so many tournaments. I’m not going to name them, but we need to have our rights because we have great players, great Top 10 players, Top 20, any other players. You can see a lot of exciting matches.

“I just wish everyone would give the opportunity to see why we deserve where we want to be paid. People need to watch us.”

Shapovalov agrees. To grow the game, players need to be seen across as many platforms as possible. The 23-year-old who represents Canada was inspired to take up the game by watching Roger Federer.

“But if women’s tennis gets less exposure,” he wrote, “the little girl in front of the TV may not think it could be a reality for her. She’ll never see her idol and go, Look at her. I want to do that.’ And that is heartbreaking.

“So let’s give everyone the same chance. Let’s pay out the same prize-money. Let’s stop talking about reducing the gender gap. If we want tennis to be fair, it should not exist at all.”

Pegula believes the joint events like the BNP Paribas Open are helping to close the gender pay gap. Both winners here receive the same $1,262,220.

“We’re better when we’re together, for sure,” Pegula said. “The joint events, they’re bigger, they’re better. Everyone gets treated better, gets treated equally and that’s ideally what we want to happen all the time in the future.

“I think it’s getting there. Obviously, it’s we still have a long ways to go. But it was nice to see him take the time to highlight that.”