We finally got a definitive outcome in the rivalry between Manny Pacquiao and Juan Manuel Marquez Saturday night on HBO pay-per-view, and in a way that rocks the sport of boxing to its core: Marquez knocked Pacquiao — one of boxing’s two biggest stars — out cold in the 6th round. It had been a thrilling back-and-forth bout prior to that, one where both men traded knockdowns.

If anyone was thought to be able to render a conclusive end to this bout, it was predicted that it would be Pacquiao, as he was the man who’s been living at welterweight for a while and has always been the bigger puncher of the two, while Marquez has only flirted with the division.

In the first two rounds, it looked very much like Pacquiao was the one who had come out with the better focus and better game plan — head movement, feints, using his legs to fire and get out. But in the 3rd, Marquez, who had been investing in body punches, feinted with a left to the body and then caught Pacquiao with a looping overhand right that legitimately dropped Pacquiao for the first time in many years.

Pacquiao recovered, though, both psychologically and physically, in the very next round, and by the 5th he gave Marquez a knockdown of his own, and a more damaging one, and after rising from that straight left, Marquez foolishly traded with Pacquiao until the bell rang in one of the best rounds of 2012.

Everything seemed to be going Pacquiao’s way in the 6th, too, until the final seconds: Pacquiao lunged forward, and Marquez, who was crouching down, thrust forward a full-force, crunching, perfect right hand that caught Pacquiao as precisely as you can catch someone. Pacquiao landed flat on his face, unconscious, and frighteningly so; I was legitimately worried that he was dead.

There might be a rematch, but this is the kind of knockout loss that Pacquiao has delivered in the past, the career-ending kind against Ricky Hatton. If it’s the end of the road for Pacquiao, he really does go down as THE fighter of this era who has the best resume.

If he rebounds from this, somehow, it will be impressive enough, but Pacquiao has enough going for himself as a politician in the Philippines that he ought to consider ending on this note and moving on to the next phase of his life. If Pacquiao is through, then we’re at the end of a period in boxing where he has been one of the sport’s signature stars. It certainly kills the viability of the mega-fight with the other signature star of this era, Floyd Mayweather.

Marquez finally gets that win that has eluded him after three previous meetings with Pacquiao. Given his association with controversial strength and conditioning coach Angel Heredia, and his cut physique at age 39, there will be those who will chalk up this victory to performance enhancing drugs.

There is no proof of any malfeasance, though, and until then all anyone has is suspicion, reasonable or no. What we do know is this: Marquez scored a career-defining win and a knockout for the ages, which will go down as one of the most memorable and meaningful KOs in the sport’s history.

Austin Arrieta | Elite.