Former world No. 1 Caroline Wozniacki has seen tennis at its cruel and beautiful best more than anyone. Sure, tennis can give you the best moments of your life, push you to your boundaries, and impart lessons that only the court can. Wozniacki lived that reality, claiming 30 WTA singles titles, but even after retiring in January 2020, one element of the game continues to bother her – a habit she believes can influence the fairness on court.

Just recently, @cate_tennis shared a clip from the podcast Nothing Major Show, where John Isner asked Wozniacki what rule change she would implement on the WTA Tour if given the opportunity. She was clearly speaking from experience when she said:

“There should be like a mic and there should be a decibel thing, so you can’t grunt over a certain level. I think that should be a rule. And also the length of the grunt. I think that would be great ’cause I was never a big grunter; I never made a lot of sounds when I was playing.” But why is grunting such a controversial issue among players?

Wozniacki, like many others, believes that it can disrupt the opposing player. “You can’t hear someone hit the ball properly when someone is screaming so loud. I think it really disturbs the opponent in some way. And I think as a fan, you don’t really want to listen to that either,” she explained.

That said, scientific studies have shown that grunting can provide tangible benefits. In addition to helping players with breathing, rhythm, and muscle engagement, it can help some players relax or maintain focus and even increase their shot power. Nevertheless, grunting remains a polarizing aspect of the game.

Like at Wimbledon 2025, for example, Aryna Sabalenka’s grunt was so loud that stadium graphics likened it to a car horn or even a lion’s roar. Sabalenka herself admitted, “Honestly, I don’t even hear myself when I am playing.” But how much does it affect those across the net?

A fair bit. The effect became obvious during the 2025 French Open quarterfinals, when Aryna Sabalenka defeated Zheng 7‑6(3), 6‑3. After the match, Zheng addressed the grunting in her press conference:

“I will say this. How can you scream when you hit the ball, but you still screaming when I hit the ball? This is hindrance.” She added that the rule needed to change and joked that next time she might “scream when she hits next time we play if nothing is done.

Which brings us back to Wozniacki’s point: Grunting at extreme volumes can make the game unfair and disrupt focus, even for top players. So the need to control grunts, she thinks, could also help instill better habits in younger players.

“Sometimes it helps the player, sometimes it doesn’t…I think that should be a rule, and the younger generation could start off by being a bit more quiet.”

Wozniacki herself has displayed in her own career that grunting loudly is not only an irritant but also a competitive disadvantage to the one being grunted at.

How grunting disrupted Caroline Wozniacki’s game at crucial moments

At the 2018 Qatar Total Open in Doha, Caroline Wozniacki, then the world number one, faced Monica Niculescu in the third round and won 7‑5, 6‑1. But during the ninth game of the first set, Wozniacki became frustrated. She felt that Niculescu’s grunts and noises were timed to distract her just as she was about to hit her shots.

Wozniacki told the umpire, “She’s a player that tries to get into your head. I just tried to let him [the umpire] know to pay attention to her grunting because she’ll hit the ball, and two seconds later, when the ball is on my side and I’m right about to hit, she’ll start grunting and make a noise, and she’ll change the grunt according to what she feels like…”

She added, “It’s disturbing. It’s in the rules that they’re not supposed to do that, so I was just making sure the umpire was paying attention to that. And she stopped doing that after.”

Wozniacki clearly felt the grunting was a deliberate tactic to interfere with her focus. But how did Niculescu respond to these accusations?

Niculescu denied any intention to distract Wozniacki. “That was very bad from her; I have never heard a number one talk like that. I am really disappointed by what she said, and I think she gives herself too much importance,” she said. She insisted that grunting was just part of her playing style and not meant to affect her opponent.

Still, for Wozniacki, the interruptions were real and challenging. Interestingly, this is the same issue that current world number one Aryna Sabalenka faces.

According to a 2023 study, Aryna Sabalenka grunted on 100% of her serves and about 95% of her rally shots. Some players, like Wozniacki, may find this annoying, but others don’t seem to mind. For instance, Coco Gauff claimed that Sabalenka’s grunts didn’t annoy her: “It didn’t bother me… If she [Aryna Sabalenka] did it extended on certain balls, then I would be like, ‘Okay, it’s ridiculous.’ No, I think that’s just her. It’s fine… It doesn’t bother me.”

This contrast shows the various effects grunting can have on players. Some find it to be a small eccentricity, while others find it extremely difficult to stay focused and on time.