Pacquiao's defeat was as scary as it was stunning. Serious questions remain about his future.
Few if any saw this coming.
It's not even that Marquez knocked Pacquiao out. Though this is a little surprising since Marquez isn't known as a devastating puncher and Pacquiao hadn't been stopped in over 13 years.
It was the sheer suddenness and violence of the knockout that left most of us stunned.
Juan Manuel Marquez landed a shot for the ages. A missile of a short right hand that landed square on the button and ended the fight the second it connected.
In those few moments between the shot landing and Manny Pacquiao finally beginning to move again, the happiness one felt for Marquez finally getting his vindication was tempered by concern for the fighter.
It was concern for a fighter who has given so much to the sport, entertained so many and accomplished so much, but who now faces an uncertain future.
Nobody is inside the head of Manny Pacquiao and he will ultimately make his own decisions. But let's analyze what some of his options are going forward after this devastating loss.
Pacquiao looked ready to take over the fight when a bolt from the blue ended his night.
Boxing is unique amongst sports.
In baseball, if your skills erode you might not be able to catch up with the high fastball anymore. Or you might lose a few mph off a pitch that used to get guys out, but now gets walloped around the field.
In boxing, when your skills erode you can get seriously hurt.
Many had speculated, even before this fight, that Manny Pacquiao was in decline. His activity rate, killer instinct and power, all of which made him the fighter he was, had all seemingly slipped.
It's natural for people to translate this knockout into further evidence that it's time for Pacquiao to retire. And they might well be correct.
It was truly scary and something nobody wants to see repeated.
But up until that point, Manny Pacquiao seemed to be taking control of the fight. He had Marquez badly hurt, broke his nose and seemed on the verge of stopping him.
Pacquiao was not done in by slipping skills, he was done in by an absolutely perfect shot from a world-class fighter.
He may well ultimately retire, but he shouldn't do it based on one performance, however devastating.
Many felt a fourth fight was excess, many of the same are no longer complaining.
When a fourth fight between Manny Pacquiao and Juan Manuel Marquez was announced, there was a lot of grumbling and complaints from boxing fans.
But the fight clearly vindicated itself. It was the best of the series, with the most action, the most drama and the most spectacular and decisive ending.
Many of those same people who were bothered by a fourth fight are now clamoring for a fifth.
And why not? If there was unfinished business before, then what do we have now?
Amazing as it seems, the one fighter who can lay claim to a decisive victory in this series is Juan Manuel Marquez.
This is something that will definitely gnaw at Manny Pacquiao who may feel that he needs a fifth bout to repair his legacy.
More important than any of this is the fundamental point that a fifth bout would be an even bigger PPV attraction than any in the series to date.
Mexican fans are rightfully charged up with this victory and a wounded Pacquiao fanbase would love nothing more than to see their hero settle the score.
Rios was the original plan if Pacquiao had gotten by Marquez.
Had Pacquiao gotten by Marquez, his next opponent was already lined up—fellow Top Rank fighter and undefeated junior welterweight sensation Brandon Rios.
It remains to be seen if Top Rank will go on with the fight as planned, scrap it entirely or potentially match Rios with Marquez.
One must wonder if Marquez would want any part of Rios. This has everything to do with Marquez' age, and limited time remaining to make money, and nothing to do with perceiving him to not want the fight.
At nearly 40 and coming off the biggest win of his career, he'll want to cash in and nobody can blame him. He might not see Rios as a big enough name to meet that goal.
Pacquiao might see Rios as a chance to get the ship righted before pursuing a fifth fight with Marquez in the Fall.
But Top Rank could see this as too great a risk and look for a softer touch if an immediate rematch can't be secured.
Bradley has been AWOL since his June "win" over Pacquiao.
Before losing to Juan Manuel Marquez, Manny Pacquiao made it very clear he had little interest in settling the score with Timothy Bradley.
This was surprising to many who felt that Pacquiao should right the obvious wrong that was done to him when Bradley was awarded a ridiculous split decision win in June.
But let's face it. Pacquiao made the right call even though Marquez starched him.
In the grander sense Pacquiao was trying to show the fans, of which there are many, who felt he couldn't beat Marquez that they were wrong.
This was more important to his overall legacy and image than avenging a loss that has been widely discredited and ridiculed in virtually every circle both in and outside the sport.
Perhaps now with a decisive defeat hung on him, he'll be more open to avenging that "loss."
Pacquiao is one of the most loved figures in the Philippines.
Manny Pacquiao is an occasional fighter but a full-time politician. He was overwhelmingly elected to represent Sarangani Province in the Filipino Congress in 2010.
In the election he received over two-thirds of the vote. This was made all the more impressive given his opponent was a member of wealthy family that had dominated politics in the region for decades.
In the Philippines, there are few people better known and more popular than the Pac-Man. He has raised his national political profile with his campaign and election to Congress and has been speculated as a future Presidential candidate.
The next Filipino Presidential Election is not until 2016 and it would be a tough road, so if he decides to run, the time to make moves could be rapidly approaching.