A small number of fights in boxing are so enthralling, so close and so entertaining that they justify a rematch to determine who is truly the better fighter.
Often, this rematch leads to a trilogy, since claiming a victory apiece rarely sits well with fighters or fans.
However, a handful of rivalries throughout history are so enthralling, and capture the imagination of fans to such a degree, that they demand a fourth fight.
One such epic encounter is that of Manny 'Pacman' Pacquiao vs Juan Manuel Marquez.
The reason this match-up was so enthralling is due to the style of each fighter.
Both guys lay it all on the line, flying forward with no regard for the scorecard, tunnel visioned with only one thing in mind, to put the other on the canvas. And they did, a lot.
Pacquiao's continuous aggression and non-stop body and feet movement made him enamoured within the sport.
An explosive southpaw with a deadly wide left hook, his one-two straight combination was a thing of legend.
Marquez encapsulated that Mexican fighting spirit. A fearless counterpuncher who could mix it up, his brutal body punches brushed many a worthy opponent aside.
Fights one and two
During the first fight, Pacquiao knocked Marquez down three times in the first round, displaying his ferocious attacking style and relentless desire to land that knockout punch.
Marquez somehow recovered, though, and the fight ended in a draw, a result which caused quite a bit of controversy mainly from Marquez's fans.
The second fight took place at Mandalay Bay four years later in 2008, a match-up Pacquiao would later describe as his toughest fight since their first encounter.
This time, Pacquiao edged a split decision. Interestingly, though, one of the judges actually scored the bout 115-112 to Marquez.
Marquez and his Mexican following felt he was robbed by the judges in both fights because he was the less popular fighter, and his style was less attractive to watch.
A good number of fight fans agreed too. Thus, the seeds were planted for a legendary rivalry which would grip boxing for years to come.
On the one hand, the gritty underdog forced to overcome what he perceived as an underlying and institutional bias, and the people's champion, obsessed with obtaining a convincing victory over a dexterous foe, to silence the haters once and for all.
By now, Pacquiao was a boxing sensation, his action-packed and free-flowing style making him one of the most popular fighters around.
Marquez remained unfazed though - he had work to do.
This was undoubtedly one of the closest title fights in the modern era.
Pacquaio started off strong, picking up two or three of the first four rounds, utilising his fast feet and excellent body movement, consistently launching that famous left jab straight down the throat of Marquez.
Marquez replied with aggressive strikes of his own, though, regularly finding a home for his counter left body punch.
Throughout the middle rounds Marquez began to edge the contest, landing a huge right on the button in the fifth, immediately followed by a perfectly-timed uppercut and right cross.
In the ninth, both guys let the hands go, raining blows in a flurry of both frantic and highly-accurate strikes.
Most people had Marquez ahead or a draw going into the final two rounds, where Marquez inexplicably took his foot off the gas.
Ultimately, Pacquiao won by majority decision, a decision which was audibly booed by the Las Vegas crowd, and which ultimately laid the foundation for their fourth and final bout.
Fight of the year, knockout of the year and round of the year! This fight did not disappoint, pulling in well over a million pay-per-view buys and not a single one could have any complaints.
It was simply an incredible fight, which mirrored their previous encounters in so many ways.
Pacquiao took the first two rounds, growing in confidence and getting more aggressive as he backed Marquez up with a beautifully-timed right hook.
Marquez, however, responded brilliantly, utilising his now famous counter-punching abilities, and in the fourth, he dropped Pacquiao for the very first time, landing a couple of vicious body punches, followed by a brilliant faint and wicked overhand right which landed flush.
As the sixth round got underway, Pacquaio had begun to control the encounter.
Marquez's nose was broken and streaming blood, the referee was keeping a close eye.
Perhaps envisioning his name in lights and the doubters silenced, Pacquiao pressed forward for the knockout.
Then it happened, with 10 seconds left in the round he overstretched and found himself exposed.
Marquez, backed against the ropes, saw his opportunity and snapped a short right which landed in the cleanest of fashions.
The champion, the fighting pride of the Philippines, fell to the canvas, face down, unmoved.
The underdog had done it, and one of the greatest rivalries in boxing history saw its final chapter close.
To be completely honest, I still can't decide who was the better fighter, but I don't feel like I need to decide.
If two champions can go head to head four times, and we can still have a legitimate argument about who was better, then all we know for sure is that we're discussing two undeniable greats of the sport.
Pacquiao & Marquez truly are that.
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