Floyd Mayweather says his fight with Conor McGregor in Las Vegas on 26 August "won't go the distance".
Mayweather, 40, has won all 49 of his professional bouts, but has not boxed since September 2015 and came out of retirement to fight the Irishman.
The 29-year-old mixed martial arts fighter has not boxed professionally.
"He's looking forward to ending the fight early, I'm looking forward to ending the fight early - it won't go the distance," said Mayweather.
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The American, whose last fight was a points victory over Andre Berto, said he will be doing his "homework" on McGregor, a two-weight world champion in the Ultimate Fighting Championship.
"It's not really watching fight tapes, it's about knowing the person you're facing across the ring from you," added Mayweather.
"You want to know what they like to eat, what they're doing when they're not in camp."
Britain's Nathan Cleverly will feature on the undercard of the Mayweather-McGregor bout, as the 30-year-old Welshman will aim to make the first defence of his WBA light-heavyweight title against Sweden's Badou Jack.