Rios, 27, meanwhile had no doubt he will beat Pacquiao, who turns 35 next month and has a record of 54 wins, five defeats and two draws in a pro-career spanning almost 19 years.
The American, a former lightweight world champion, declared he was in the shape of his life and should not be written off as merely a a “tune-up” for Pacquiao, who needs a victory after consecutive losses to Timothy Bradley and Juan Manuel Marquez last year.
“They think I’m no problem,” Rios said, looking at the Pacquiao entourage.
“I’m nobody’s tune-up fight. I’m nobody’s punching bag – a punching bag don’t punch back. Sunday you’re going to find out I’m not going to stop. I’m a monster when I get in that ring.”