By Carlos Boogs

There was a moment in time when eight division world champion Manny Pacquiao (58-6-2, 38KOs) was demolishing his competition inside the distance.

While Pacquiao has looked impressive in the ring, his victories have been lacking the same devastation that we've seen in the past.

The last time Pacquiao scored a knockout victory was in the fall of 2009, when he stopped Miguel Cotto in the twelfth round.

This coming Saturday night, Pacquiao will challenge WBO welterweight champion Jessie Vargas (27-1, 10KOs) at the Thomas & Mack Center in Las Vegas.

The Filipino's star head trainer, Freddie Roach, is predicting a knockout victory. The problem is, fans don't believe him anymore - because Roach has made similar pre-fight predictions for the last few years.

According to Pacquiao, the reason for his lack of knockouts is the fact that he's fighting at an unnatural weight against much bigger opponents. Pacquiao says he's fully capable of making the lightweight limit of 135-pounds and his natural weight is 140-pounds. He basically eats his way to the welterweight limit of 147.

"Remember my minimum weight is – I can still make 135.  I can still make 135 and my natural weight is 140.  When I move up into the higher weight divisions it changes my preparation – I eat a lot to make 147.  Where I may gain a pound of two between the weigh-in and the fight, my opponent may be a lot heavier," Pacquiao said.

"I am not saying that I cannot [get the knockout], but what I am trying to do in every fight I try to do my best.  It just so happens that my opponent is tough and bigger than me.  But I am still trying to do my best to get a knockout in the fight.  I am not saying what I am predicting for this fight but if the knockout comes, it will come – it is the bonus for all of your sacrifices in training."

"My opponent is bigger than me but that doesn’t matter – I am not disappointing the fans that I have and I did my best.  I work hard in the fight and in training and I have proven that to the fans."

Pacquiao's promoter, Bob Arum of Top Rank, has his own explanation on the subject. In his opinion, many of Pacquiao's opponents become defensive once they taste his power. Arum doesn't expect Vargas to get defensive, he expects him to trade.

"There is another factor.  The fighters that Manny is fighting, because he is so powerful and he throws so many punches and he throws them in bunches and he hurts guys – is that they tend to fight in defense.  Now any fighter or trainer will tell you that if that happens it is very difficult to knock somebody out – very difficult," Arum said.

"I think with Jessie Vargas, who is an offensive fighter who is going to go after Manny, whose goal is to knock Manny out – I think you will see, one way or another, a knockout in this fight.  And it’s a lot because Jessie will be fearless and some people say reckless, will be going after Manny to try and knock Manny out.  And when that happens it is easier for the other to knock that guy out – you know that."