The Filipino boxer has put together an amazing career that has seen him win multiple titles and climb up the rankings as the best pound-for-pound boxer in the world.
In almost 20 years as a professional, he has a career record of 54-5-2. Unfortunately, a knockout loss to Marquez after losing to Timothy Bradley could end this illustrious run.
There are a few reasons that Saturday's fight should be his last, but the primary one is a lack of qualified opponents.
A couple of years ago, all anyone in the boxing world could talk about was the possibility of a fight between Pacquiao and Floyd Mayweather. This dream scenario would pit the two best boxers in the world against each other, and it would generate a ton of revenue.
Unfortunately, one of the best in the history of the sport would not want to risk his legacy against someone coming off two losses in a year. Pacquiao still has an incredible amount of talent, but his record no longer makes him worthy of such a big match.
At the same time, Pac-Man does not want to choose a random opponent that he will easily beat just to fill a date. Fans would understand the purpose and have little interest in seeing it.
This leaves yet another rematch with Marquez as one of the only remaining options. Pacquiao was likely on his way to winning another decision before being caught by a big right hand. He needs to prove that this was only a fluke.
However, there is no guarantee that Dinamita would want anything to do with a fifth fight between the two rivals.
Marquez and his supporters believed that he truly won each of the first three fights, despite them resulting in a draw and two losses. This knockout justifies that theory, and it helps define his career as one of the best in this generation.
Another fight could only hurt this perception. The smart move would be to end this rivalry on a high note.
The only other possible fight that Pacquiao could set up is a rematch against Bradley, but it might not be worth it for Pacquiao to come out for another possible loss.
Instead, the veteran boxer should end his career on a not-so-high note before things get worse.
One of the biggest issues in the past few years has been what seems like a lack of focus. Among other things, Pacquiao has been juggling a boxing career, a political career and his newfound appreciation for religion, which he discusses in an interview with ESPN's Jeremy Schaap.
It seems to have taken a toll on the fighter, and he has not had the same intensity during his matches that he used to show. If his passion for boxing is gone, he should not remain in the ring.
On the other hand, this shows that he has other things going for him besides boxing. It does not make sense to risk further injuries that could do permanent damage.
Few in boxing have been better than Manny Pacquiao over the past decade. He has already proven that he is one of the best of all time, and he does not need to add anything else to his legacy.
This would be a perfect time to call it a career and retire from boxing.