By Alan Baldwin
Ruiz, dubbed the "Quietman," went down on one knee twice more in the fifth and sixth rounds before his corner threw in the towel for Panamanian referee Guillermo Perez to stop the contest after two minutes and a second of the ninth.
"I think I've got it all and I can prove myself against the best guys," Haye, now 24-1-0, told Sky television at ringside.
"If I hit them with the same shots I was hitting John Ruiz, both of those two would go over."
"I knew it was going to be tough, I knew when I did land my bombs I would hurt him, but he's not the type of guy to get knocked spark out," gasped Haye of a bloodied opponent, who made up in stubborn determination for what he lacked in speed and movement.
"I knew it would go something like that, I didn't anticipate getting hit as much as I did in that fight but credit to John Ruiz.
"I believe I am the most exciting heavyweight in the world and even against John Ruiz I can make it exciting," added the 29-year-old after winning only his fourth bout as a heavyweight.
Haye, wearing his allegiance on his shorts in the colors of the British flag, looked like he was going to make swift work of Ruiz from the opening bell when he decked the American with a stinging right after just 25 seconds.
Ruiz went down again later in the round for a second count, although Haye was penalized after the referee deemed it had been from an illegal blow.
"I think I could have got him out in the first round if I'd took my time," said Haye, who sauntered into the arena calmly, milking the applause against a fiery backdrop. "But he's an experienced guy so I'll give him the credit.
"I enjoyed the fight and enjoyed the crowd and at no stage in that fight did I feel like I was losing.
(Reporting by Alan Baldwin; Editing by Peter Rutherford)