Sunday morningWelterweight title fightPacquiao     vs     Rios (12 Rounds) 4am-:30am SS6MACAU. Brandon Rios has warned Manny Pacquiao he will be facing a ‘monster’ in the ring on Saturday night.The two welterweights clash in the gambling mecca of Macau with both bidding to bounce back from defeats. And Rios believes his opponent is in danger of underestimating him.‘This will be one of the biggest days of my life,’ he said. ‘They think I’m no problem but I’m going to be a huge problem. ‘This camp is the best I’ve ever had. I’ve been disciplined; I’ve followed my diet and done everything I need to win. ‘Everyone thinks I’m a tune-up fight; I’m nobody’s tune-up fight and nobody’s punch bag.  ‘I’m a monster when I get in that ring.’Pacquaio, whose trainer Freddie Roach was involved in a bust-up on Wednesday morning, insisted he is desperate to return to winning ways after his brutal defeat to Juan Manuel Marquez last year.‘I have prepared for this fight and he has prepared for this fight; let it be finished in the ring,’ he said.‘I have lost twice and I’m doing my best to win the fight especially after what happened in the Philippines with the typhoon.’Pacquiao, a former champion in eight divisions, has to win the fight for the vacant WBO international welterweight title to prove he is not over the hill. And he has to win well, too.The 34-year-old Pacquiao has a professional record of 54-5-2, including 38 wins inside the distance. But he lost on points to Timothy Bradley in June last year and was knocked stone cold in the sixth round by Marquez in December.Rios comes in with a record of 31-1-1, with 23 knockouts. The man from Oxnard in California is a former WBA lightweight champion but suffered his first defeat in March this year when Mike Alvarado beat him on points in a return match. In their first fight he knocked out Alvarado in the seventh round.There are definite signs that Pacquiao has slowed down. He has not won by a knockout in his last six fights, which brought him four points victories and two defeats.His combination of power and speed, and the use of angles around the ring have been missing for too long now. The last time he won inside the distance was against Miguel Cotto in November 2009