"I am always ready for 12 rounds," the "Russian Giant" said in an interview with Russian Sports TV channel. "Ruiz has great stamina like a punch bag."
The 35-year-old Russian (48-1, 34KOs) also said about "The Quiet Man" Ruiz's tactics (43-7, 29KOs), "I think he will be snatching the distance and clinching."
Valuev became the first Russian world heavyweight champion in December 2005 when he defeated Ruiz. In April last year he lost his title to Ruslan "White Tyson" Chagaev from Uzbekistan.
Since then Chagaev has defended his title once, but a torn achilles tendon forced a delay in his mandatory challenge bout against Valuev. On July 4, the WBA decided to sanction a match against the Russian's closest contender, "The Quiet Man."
In a recent interview with BoxingScene.com website, Chagaev said he was on his way to recovery following tendon surgery. He was cautious about who would win in the upcoming bout, but said he would prefer to fight Valuev in his title defense.
"In my opinion the better boxer should win," the website quoted Chagaev as saying. "[I would rather fight] Valuev, because unfortunately I had to cancel the two scheduled dates for our fight because of my illness in May and then the accident with my left foot at the end of June."
Chagaev is currently what the WBA calls a "champion in recess," and the winner of the Valuev-Ruiz fight will have to face Chagaev before June 26, 2009, if the Uzbek manages to get fighting fit by then.