A victory would bring Pacquiao's name back to the win column after a loss to Timothy Bradley that was shrouded in controversy and possibly set up the world's dream bout against Floyd Mayweather. On the other hand, a loss could siphon all the years worth of excitement out of a possible Mayweather bout and leave many questioning whether Pacquiao is still a pound-for-pound great.
If that happens, and you're looking for a scapegoat reasoning, look no further than Pacquiao's political career.
Since becoming a congressman in his native Philippines in 2010, the 33-year-old southpaw is 3-1, with the one loss coming against Bradley. More notable than anything from those fights is that Pacquiao has not won via knockout in those contests.
Granted, there are many plausible excuses one could use as justification.
There is the distinct possibility that as he's gotten older, Pacquiao is just becoming smarter about the punches he takes and thus taking less knockout-worthy chances in the ring. You can also make the case that it's such a limited sample size that the statistical significance of those fights is negligible. Some rational fight fans simply believe that Pacquiao's lack of knockouts simply comes from an uptick in competition.
Those are all wholly plausible rationalizations.
Pacquiao's own camp hasn't exactly been thrilled with his efforts since becoming a congressman. Freddie Roach famously called Pacquiao out before his fight against Antonio Margarito, and fans have wondered in the fights since about his commitment to the sport.
That isn't to say any of Pacquiao's life changes are bad or anything of the sort. It's no one's place to tell another person what to do with their life, regardless of how breathtakingly spectacular they are to watch punch another human being.
Pacquiao is just a different fighter since joining the political realm. Whether that has to do with his ever-growing list of responsibilities pulling him in different directions or simple age regression, the timing coincidence is jarring.
For what it's worth, he has seemed more focused heading into Saturday.
That still hasn't stopped the doubters. Even strength trainer Alex Ariza is concerned that Pacquiao is not preparing for the fight in the correct way, as the Filipino star has eschewed strength and conditioning this time around.
Nevertheless, even if his preparation works out and he pounds Marquez into the mat, it won't change Pacquiao's encroaching interests.
Perhaps it was Pacquiao himself who said it in his Business Week column on June 7. Speaking on his lifestyle change and emphasis on politics, Pacquiao made it quite clear where the future is heading: "Boxing is my passion. Public service is my calling."
We've noticed, Pac-Man.