How serious is Floyd Mayweather about running it back one mo' gin with Manny Pacquiao?
According to the top guy at Showtime Sports, he's serious as a heart attack ... as in DEADLY SERIOUS.
TMZ Sports talked to Stephen Espinoza -- Prez of programming for Showtime Sports (and Conor McGregor's archnemesis) -- about the proposed rematch, and if would ever ACTUALLY happen.
"Having spoken to Floyd, I know he's deadly serious about it. He's very, very serious about wanting the fight.