The sixth round of the Juan Manuel Marquez vs. Manny Pacquiao fight on December 8 was the defining moment of Marquez's career.
The great Mexican fighter had been tormented by his rivalry with Manny Pacquiao. In three previous fights, Marquez had stayed close but was not able to come away with a victory.
He brought an 0-2-1 record into his fourth fight in the series. Marquez, 39, appeared stronger and more powerful for the matchup with Pacquiao than he had at any point in his career.
While many fighters have shown they can compete at a high level after the age of 35, they don't often gain musculature and definition at such an advanced age.
Marquez was a confident fighter when he stepped into the ring. As the fight moved along, he landed a hard overhand right in the third round high on Pacquiao's head and sent him to the canvas with a thud.
Pacquiao also registered his own knockdown of Marquez and had appeared to win every round but the third.
That included the sixth round—at least up until the final seconds. Pacquiao had hit Marquez with shot after shot and Marquez was bleeding from the nose and mouth.
Pacquiao may have thought he could finish Marquez off and he moved closer. However, just as soon as Pacquiao got in range, Marquez delivered the hardest punch of his career on his rival's chin.
Pacquiao went down face first. He was knocked unconscious and Marquez had the huge win over Pacquiao he wanted so badly.
Questions have been piling up since the dramatic win. How could Marquez knock Pacquiao down twice in six rounds when he couldn't knock him down once in 36 previous rounds?
How was Marquez able to add so much muscle? Where did the added definition come from?
Those questions are pointed because Marquez is affiliated with strength training coach Angel "Memo" Heredia, who is also known as Angel Hernandez.
A Los Angeles Times story cited a report by an independent arbitrator assigned by the U.S. Anti-Doping Agency that called Heredia an "admitted drug dealer." According to the report, Heredia has said that he gave performance-enhancing drugs (PEDs) to "two dozen elite athlete athletes."
Heredia now says that his training methods are clean and he no longer uses PEDs to get his athletes in top condition.
Marquez took a Nevada State Athletic Commission pre-fight drug test and the results are likely to be released in the next few days. Marquez says the test will reveal that he is clean and he didn't take any PEDs.
However, the association with Heredia will hang over his head. Heredia was labeled a "controversial strength and conditioning coach" by Pacquiao's trainer Freddie Roach.
Heredia said that Marquez was able to increase his strength, power and definition through legal supplements like "creatine and amino acids."
It's not easy to take Heredia at his word; cheaters are usually one or two steps ahead of detection methods.
Marquez had to know he would come under scrutiny when he chose to be associated with Heredia. The questions will not go away, no matter how many clean tests he has from this point forward.
Marquez's greatest victory is tainted by his association with a controversial strength coach whom he should have known to stay away from.