According to the The New York Post Piazza has an idea how the rumors started but does not give names
He does say however that they began in 2002, when Mets manager Bobby Valentine said that Major League Baseball was ready for an openly gay player.
“The whole episode was such a strange, incredible phenomenon… I still don’t get it. I don’t know where the rumor came from, although I’ve heard many theories, including one that I suppose makes the most sense to me, involving a former teammate and his agent.”
“I’m not gay. I’m heterosexual. I can’t control what people think. I can say I’m heterosexual. I date women. That’s pretty much it.”
Questions about his sexuality bothered him less than the insinuation that he was somehow phony.
“I found it hugely insulting that people believed I’d go so far out of my way — living with Playmates, vacationing with actresses, showing up at nightclubs — to act out a lifestyle that would amount to a charade,” he writes. “If I was gay, I’d be gay all the way.”
“I’d be gay all the way” Love it!