Controversial tennis star Maria Sharapova says Serena Williams’ dominance over her stems from Wimbledon 2004 – when the Russian heard the American sobbing in the locker room after an upset defeat in the final.

In New York Times extracts of her new memoir Unstoppable: My Life So Far, which is being released on Wednesday (AEST), Sharapova says her breakthrough at the All England Club steeled Williams, who has won the past 18 matches between the pair.

Sharapova said Williams was an intimidating figure, but let her guard down after the match.

“Guttural sobs, the sort that make you heave for air, the sort that scares you,” Sharapova writes of the aftermath.

“It went on and on. I got out as quickly as I could, but she knew I was there. People often wonder why I have had so much trouble beating Serena; she’s owned me in the past ten years …

“In analysing this, people talk about Serena’s strength, her serve and confidence, how her particular game matches up to my particular game, and, sure there is truth to all of that; but, to me, the real answer was there, in this locker room, where I was changing and she was bawling.

“I think Serena hated me for being the skinny kid who beat her, against all odds, at Wimbledon.”

Serena Williams has dominated Maria Sharapova, winning their last 18 encounters. Photo: Getty

The New York Times said that Williams’ agent Jill Smoller did not respond to calls seeking comment on the extract.

Sharapova returned to tennis in April after a 15-month ban for failing a drugs test in 2016. She had been taking meldonium, prescribed by her doctor, but which had been put on the banned performance-enhancing list only months prior to her positive test.

Watching Serena from a knothole in a shed

Sharapova said as a 12-year-old her father organised for her to watch the Williams sisters training from a clandestine spot in a shed because she did not want to be seen to be a fan sitting in the stands.

“I could watch through a kind of knothole – just me alone, in the dark, seeing the next 20 years of my life,” Sharapova writes.

“Her physical presence is much stronger and bigger than you realise watching TV,” Sharapova writes of Serena. “She has thick arms and thick legs and is so intimidating and strong. And tall, really tall.”

And the Russian acknowledges that the relationship with her rival is not friendly.

“Serena and I should be friends: we love the same thing, we have the same passion,” she writes.

“Only a few people in the world know what we know – what it feels like in the dead centre of this storm, the fear and anger that drive you, how it is to win and how it is to lose. But we are not friends – not at all.

“I think, to some extent, we have driven each other. Maybe that’s better than being friends. Maybe that’s what it takes to fire up the proper fury.

“Only when you have that intense antagonism can you find the strength to finish her off. But who knows? Someday, when all this is in our past, maybe we’ll become friends. Or not. You never can tell.”