Alex Rodriguez allegedly confessed his love for Madonna at the beginning of this year.
The New York Yankees baseball star - whose close relationship with the singer is a factor in his recent split from wife Cynthia, her lawyers claim - told a pal he was besotted with Madonna as they had dinner at a restaurant in January, during which Alex spent most of the evening texting her.
His friend told Us Weekly magazine: "He kept smiling, acting as if he was a little kid. He told me it was Madonna he was texting. I was shocked. He proceeded to say he was in love with her. I thought he was kidding but he wasn't."
Just a few weeks after the dinner, Alex - who has two children with estranged wife Cynthia - confirmed how much he had fallen for Madonna, telling the same friend: "She's my f***ing soulmate."
Madonna - whose own marriage to director Guy Ritchie is allegedly on the brink of collapse - has previously denied any involvement with the sportsman, insisting they are just friends.
She was also furious her alleged relationship with Alex had been labelled an "affair of the heart" by a lawyer for his wife.
A source involved with the divorce said: "Madonna is outraged. She told his wife Cynthia's lawyers not to make any more statements about her - in short, shut up."
Cynthia's legal team served her spouse with divorce papers earlier this week.
Despite not being named in the documents, Cynthia's lawyers are still attributing some of the blame for the break-up to Madonna.
One of Cynthia's legal representatives, Earle Lilly, said of Madonna and Alex: "The correct analysis is a relationship. Some people categorise an affair as sexual infidelity. We're not claiming that - it's an affair of the heart."
Madonna's spokeswoman yet again played down reports the singer and Guy - who raise three children together - were set to split.