Former world heavyweight champion Mike Tyson says David Haye lacks the punching power to defeat Wladimir Klitschko.
Haye, the WBA king, faces IBF and WBO champion Klitschko at Hamburg's 45,000-capacity Imtech Arena on Saturday.
"David has never shown the punching power to force a guy of Klitschko's calibre into reverse gear," said Tyson.
"I don't say this to disrespect Haye but as an objective observer. This is a two- or three-round fight."
Ukrainian Klitschko, 35, goes into the fight as favourite and insists Londoner Haye, 30, will become his 50th knockout victim.
Tyson became the youngest-ever world heavyweight champion in 1986, when, aged 20, he knocked out Trevor Berbick in round two.
The American, 45, went on to become undisupted champion, adding the WBA and IBF titles to his WBC crown.
His last title bout came in June 2002, when he was stopped by Britain's Lennox Lewis in the eighth round.