"Faster than Joe?" asked a media man. "Faster than Muhammad Ali!" was the reply.
There is no doubt that he has fast hands - but he also has footwork and, apparently, power and timing. His clash against the similarly quick Parker, 24, has all the makings of a classic.
Ruiz Jr, who once again appeared relaxed despite the crush of cameras and reporters around him, said he would surprise Parker with his new speed and stamina after losing more than 15kg for the fight.
He has often struggled with his weight since getting into the sport as a self-confessed "chubby" six-year-old. But now he said he is struggling no more, although his true condition will be revealed at Friday's weigh-in.
"It's going to affect Parker because I'm going to be faster on my feet," he said. "They say that I have slow feet but they're going to see the difference."
Before his "training session", Ruiz Jr was pictured with the sparkling new WBO belt. Unlike Parker, who refused to touch it or even get near it due to superstition, Ruiz Jr had no such hesitation, draping it over his right shoulder at one stage.
"I'm not leaving New Zealand without this," he said. "This is motivation right here. Pray to God, this will be mine."
Parker isn't likely to be surprised by Ruiz Jr's commitment, or his new speed - and his opponent was already fast.
But the 27-year-old's trainer Ben Lira, Abel Sanchez's assistant, said Ruiz Jr had surprised him with his improvement at Sanchez's Summit gym at Big Bear Lake, California.
"Coming down in weight, he has found out his endurance is better and of course being in Big Bear with the high altitude in the beginning stages it's real hard but he's adapted," Lira said. "We've had to push him to go further and further but he's done all that.
"That dropping of the weight has given him more speed and more stamina."
Ruiz Jr said of Lira, a veteran who is training him while Sanchez travels to Auckland from Moscow where he took cruiserweight Murat Gassiev to a world title at the weekend, said: "He's a legend, he's been in the game for a little bit more than 50 years, I'm happy to have him in my corner."
Asked about his father's Ali reference, Ruiz Jr replied: "Respect to Muhammad Ali, he was the greatest, he was the best, I admired him. Mike Tyson, [Evander] Holyfield. All I want is to be like one of them, I want that legacy, that name."