BERLIN—At the request of event sponsors as well as his promoter Don King, World Boxing Association heavyweight champion John Ruiz has backed off his earlier guarantee of a "lights-out, no-contest, 25-second drubbing" of challenger Nicolay Valuev in this weekend's title bout. "When I said that I would make short, uninteresting work of my opponent, I failed to take into account Valuev's 325-pound frame, his world-famous endurance, and the fact that fans are paying to see a good, clean, back-and-forth, multi-round fight during which many advertisements can be shown," Ruiz said. "I promise that, after many surprising second winds on both our parts and some shocking punches that I'll be on the giving and receiving end of, this will be a fulfilling, enjoyable battle, no matter who wins." Ruiz is expected to hold yet another press conference Friday to revise his new pledge that the "fight will continue for the duration of the 12 rounds, at which point the better man will win on points."