"He was a young fighter, but with extraordinary qualities," said Diaz, who at that time was a member of the Cuban boxing team's coaching staff. "I told [trainer] Alcides Segarra and several of our fighters not to lose sight of him, that he had a future in professional boxing."
A key aspect of Diaz's success in the short time he has been working with Cotto has been reminding the fighter of all the qualities that landed him among the best pound-for-pound fighters of his generation in the first place. Diaz has also worked on adding physical strength to a fighter who, at 32, is approaching the end of his career.
"For a trainer, doing technical work for Cotto shouldn't be difficult," Diaz said. "He's an athlete who has all the abilities and when we saw him [in Colombia], we saw a high-quality athlete in very good physical condition. We want to revive those things he had in his youth."
It all started with last year's rematch against Antonio Margarito. Diaz, a veteran of more than 20 years with the Cuban national team, figured that to beat Margarito, Cotto would need to return to the style that made him a silver-medal winner at the 1998 junior world championships and, as an undefeated professional, a world titleholder in 2004.
"When we started with Miguel, I told him that Margarito could be beaten if he used his feet and intelligence, not with hands and body," Diaz said. "Margarito is a very strong fighter who goes ahead relentlessly. The only way to counteract that strength is with leg movement, those that make you go back and forth. That's what we did, and what we have done in the following fights -- bring back the Miguel Cotto of 1997. We created a working model that may not be the most traditional, but it has paid off."
The boxing world was shocked in October 2011 when Cotto decided to let go of Hall of Fame trainer Emanuel Steward and hire Diaz.
"At this point in my career, Pedro Luis is the most suitable trainer," Cotto said. "He has worked me into tremendous condition and has revived my passion for boxing. I feel that he is one of the reasons, perhaps the main reason, for me to keep fighting."
"I learned a lot from Emanuel and I miss the barbecues in training camp," said Cotto of Steward, the legendary cornerman and owner of Detroit's Kronk Gym who died Oct. 25. "But right now, I need someone like Pedro Luis in my corner."
Diaz has relied on his philosophy of fitness to help breathe life into Cotto's career. At the gym where he works in Miami, a sign reads, "Discipline, dedication and desire." Cotto's desire sagged to a low point in his career, after his father's death in Jaunary 2010, but Diaz has helped him recover some of his passion for fighting.
"All we have done is applied training technology and established a harmonious relationship between him as a competitor and us as trainers," Diaz said. "We are a team. I think that has been a major factor -- one thing that was said very clearly from the first time we spoke. Working on the basis of discipline, dedication and desire leads to success.
"We work weights, strength, endurance, speed on the track, in the gym, in the ring, but without neglecting the technical side. The result is a faster, stronger and more competitive fighter. The older he gets, the more we need to focus on his strength. The work on his legs improved the coordination, and that helped so much in his two fights with Margarito."
Another of Cotto's improvements that Diaz deserves credit for is a higher aerobic. It was Diaz who persuaded Cotto to train at Big Bear Mountain, a California resort more than 8,000 feet above sea level.
"It was a very big positive," Diaz said. "A lot of people felt it was strange that Cotto had never done any altitude training. It's no secret since the '60s how this type of work can help in terms of strength and durability. That's why the training center of the U.S. Olympic team is in Colorado Springs and the Mexican team trains in [the mountains of] Toluca."
Results are pending, of course. We'll know just how effective this training has been for Cotto after Saturday night's fight against Austin Trout in Madison Square Garden. But Diaz has no doubt that the change will make Cotto a better fighter over the long haul -- if he continues with the work.
"We have seen the results, from a functional and physical point of view," Diaz said of Cotto. "Through this kind of training, we are trying to lift his spirit, rejuvenate him physically. So we gave him the altitude training to oxygenate his blood so that it can prolong his career."