The Oxnard, Calif., fighter had been all but guaranteed a shot at Pacquiao in April and a chance at headlining a pay-per-view card for the first time in his career.
Rios expected a good back-and-forth fight, one in which he believed Pacquiao would once again emerge victorious by a close split decision.
"I knew that it was going to be a tremendous fight, but I didn't know it was going to be like that," Rios said. "I knew there was going to be knockdowns, I figured that."
What he didn't figure was that Juan Manuel Marquez would score what is mostly likely going to be the knockout of the year in what could be the fight of the year over the sport's reigning poster boy.
"Wow, it was just unbelievable, man, the way Marquez knocked him out," Rios said. "The way I seen it—it was the same way Pacquiao knocked Ricky Hatton out that Marquez knocked Pacquiao out—it was just unbelievable.
"I jumped out of my seat and was like 'get up, get up, get up,'" Rios said as he watched millions of dollars and his chance at superstardom lay unconscious on the canvas.
"I told my wife, 'it (feels) like I lost a fight,' I didn't but it feels like it," Rios added. "I was supposed to fight Pacquiao, it feels like I lost a fight.
"It was very devastating because the fact that I really wanted to fight Pacquiao. I wanted to show everybody what I could do. I am ready man, it's my time, I have been doing this for a long time and it's my time to shine."
Rios knows that if by some stroke of luck he's able to somehow still get a fight with Pacquiao in April that a win over the Filipino would be great, but it wouldn't be what it once was.
"A win over Pacquiao would still bring my name up," Rios said, adding that he wants to fight the best and the best right now, in his opinion, is Pacquiao conquerer Juan Manuel Marquez.
"I thought Pacquiao was one of the best until he got dropped. Hopefully Marquez will give me a chance and me and him fight it out."
Michael Walters is a Featured Columnist for Bleacher Report. Unless otherwise noted, all quotes were obtained firsthand.