Briton Haye, 29, who defeated towering Russian Nikolai Valuev in Nuremberg in November, will fight the 38-year-old American on April 3.
Ruiz, known as “The Quietman”, lived up to his nickname when he failed to show up to the news conference announcing the fight in Manchester yesterday.
“We sent him first-class tickets and booked him into a very nice hotel but he’s not here, maybe he’s in an intensive training camp,” Haye said.
“I think Ruiz is very under-rated. In 50-odd fights he has only been stopped once, he’s always grinding people down. He is used to being the small guy in the fight, he’s fought some big guys, and he seems to find a way to smudge their work.
“This fight will be completely different to the Valuev fight. He’s the same size as me, a lot faster than my prior opponent and I’m looking at boxing a completely different fight.”
Ruiz held the title from March 2001-March 2003 and February 2004-December 2005 and is sure to test Haye’s capabilities.
Haye’s trainer Adam Booth said they would be taking his threat very seriously. “John Ruiz has been at world level for a very long time and he is the master of making talented fighters look less than ordinary,” he said.
“He’s done it throughout his career. David and I both know that this fight is a massive banana skin in David’s plans of staying world champion and unifying the titles. Looking beyond John Ruiz would be the biggest mistake we could ever make and we are certainly not going to do that.”
Haye said he was looking forward to fighting on home soil
“Now it’s time to showcase my skills again in front of the great British public and I’m delighted to have the fight at Manchester’s MEN Arena,” he told Sky Sports.
“I’ve been there on many nights to watch Ricky Hatton, Joe Calzaghe, even Mike Tyson, and the atmosphere was always tremendous.”