Mattingly was asked before Miami's game at the Washington Nationals on Wednesday about a report on FoxBusiness.com that said Jeter and former Florida governor Jeb Bush were among those who could try to buy the Marlins from Jeffrey Loria.
Reached by ESPN on Wednesday, Marlins president David Samson declined comment. Samson had said in February that multiple groups were interested in purchasing the club.
The Marlins are believed to be worth more than $1 billion.
Jeter doesn't have the capital to be the main investor in a Marlins bid. He made about $400 million in salary and endorsements during his 20-year playing career, with a net of about $220 million after taxes.
Mattingly said he is "sure" Jeter would be a good owner, because he "pretty much seems to be good at everything that he tries to do."
"He's always talked about it," Mattingly said. "I asked if he wanted to coach, and he's like, 'Never."
The two were briefly Yankees teammates in 1995, Mattingly's last season in the majors and Jeter's first, and Mattingly went on to coach New York during Jeter's stay.
Mattingly said they speak about once a year.
Jeter's agent, Casey Close, did not return a call from ESPN seeking comment.
The Associated Press and ESPN's Darren Rovell contributed to this report.