"I will not be blackmailed. I will not have my family dragged through the mud and filth," Sheffield said in a statement released by his agent, Rufus Williams.
In the statement, the Yankee outfielder said his wife, DeLeon, a gospel singer, "had a long-term relationship with a well known professional singer over 10 years ago," before the couple married, and that he had already known about it.
"I have not seen the alleged videotape, nor do I care to," Sheffield said in the statement. "I love my wife and I vow again to stand by her through any trial or tribulation."
"I do care that our privacy is respected and that the FBI and the legal authorities prosecute this man to the full extent of the law," Sheffield said.
Derrick Mosley, 38, a Chicago man who describes himself as a minister and has fashioned himself as a community activist, was charged Monday with operating a scheme to defraud for allegedly attempting to extort money from the athlete.
Mosley was in custody Tuesday pending a bond hearing. His attorney had no immediate comment after his arrest and a message left at his office late Tuesday was not immediately returned.
Williams said he had been contacted earlier this month by Mosley about a videotape purported to show Sheffield's wife. He said he called the FBI immediately.
Neither Williams nor the FBI affidavit accompanying charges against Mosley identified the musician.
Sheffield said in his statement that he was out of the country, would not be available for comment and would not discuss the matter again publicly.
The FBI affidavit does not name Sheffield, referring only to a professional athlete and his wife, and does not say whether the videotapes actually existed or whether Mosley's alleged remarks might have been part of a bluff.
According to the affidavit, Mosley first contacted Williams on Nov. 3, and Williams secretly taped several conversations with him over the next week.
In the first conversation, "Mosley stated that he was very upset and concerned about the tapes," the affidavit says. "Mosley further stated that he wished to speak to Individual A about reform and her moral standing."
Mosley later suggested he be hired for $20,000 to serve as a counselor for the athlete's wife and said he would destroy the tapes, according to the affidavit. At one point he told Williams "someone else would have called the tabloids and could have made millions," according to the affidavit.
Mosley was charged with bank fraud in 1999, pleaded guilty and was sentenced to one year and placed on probation for five years.