Don Turner wore a wry smile as he sat on the couch in his suburban Philadelphia townhouse, watching a videotape of Evander Holyfield's upset knockout of Mike Tyson from November 1996. Turner trained Holyfield for the fight and was entitled to gloat. Most pundits considered the bout virtually a suicide mission, and Nevada sports books set an early line favoring Tyson by a staggering 18-1 margin. Jay Larkin, then head of Showtime boxing, spent many a sleepless night leading up to the fight, worrying that he might have made a tragic mistake by agreeing to broadcast it.

Turner frequently paused the tape so he could explain what he had told Holyfield to do and why. Then he would hit the play button and watch Evander execute the fight plan like a programmed cyborg. It wasn't complicated stuff: Striking back the instant Tyson landed a punch was key -- and it was the last thing Turner said to Holyfield before the opening bell. As it turned out, the plan worked, the sports books took a worse beating than Tyson, and Turner's faith in the underdog was vindicated.

"I can tell most fighters how to win a fight," Turner said. "The problem is that most of them don't have the balls to do what I tell 'em to do. Evander does."

The relationship between fighter and trainer creates a unique dynamic. It's complex and multifaceted, and when it all meshes the way it did for Turner and Holyfield, a helpless cause can turn into a triumph. But that's the best-case scenario. Every fight is different and presents its owns set of difficulties. Sometimes an overabundance of courage is the problem, not a lack of it.

That was the dilemma facing Joel Diaz and Freddie Roach last Saturday when Timothy Bradley Jr. and Ruslan Provodnikov waged a magnificent struggle of unadulterated ferocity. Both men endured dreadful punishment, and there were times when Roach, Provodnikov's trainer, and his counterpart Diaz each considered stopping the fight.

"There was a point when [Bradley] came to the corner and was dazed, and I had to make a decision," Diaz said. "At those moments, I can't break. I've got to be strong. I even had to slap him a few times to wake him up. He was hurt and I had to wake him up."

In a best-case scenario for trainer and fighter, Evander Holyfield followed Don Turner's blueprint to perfection in his upset of Mike Tyson in 1996. John Gurzinski/AFP/Getty Images

It was much the same way for Roach, who practically begged Provodnikov to "show me you're OK" on several occasions in the later rounds.

Ultimately Roach and Diaz, along with referee Pat Russell, allowed the fight to continue -- a decision that delighted the fans in attendance and HBO's viewing audience. Together, Bradley and Provodnikov created something special. Whether or not letting the fight go the scheduled 12 rounds was the correct choice as far as their health is concerned is another matter altogether. The last thing a fighter needs is a trainer who is braver than he is.

Trainers often use the word "we" when referring to themselves and the fighters they work with, and although they are a team, it is far from an equal partnership. The fighter makes all the sacrifices, takes all the punches, tortures his body through a career's worth of training camps and often suffers the long-term effects of absorbing punches. True, the fighters takes the lion's share of the purse, but he or she has just one career -- and usually a brief one at that -- while a trainer can ply his trade for as long as he can attract clients.

Selecting a trainer is a lot like picking a spouse: Sometimes you get lucky right from the get-go, the way Marvin Hagler and the Petronelli brothers did, for example; but more often than not, there's quite a lot of trial and error. It is certainly not a one-size-fits-all situation. Just because a trainer has success with one fighter doesn't necessarily mean he will have success with another.

Understandably, fighters often gravitate toward a trainer with a hot hand. Roach, for example, won trainer of the year honors from the Boxing Writers Association of America five times from 2003 to 2010, most notably for his work with Manny Pacquiao. Fighters from around the world flocked to Roach's Wild Card Gym in Hollywood, and many of them did well -- not as well as Pacquiao, of course, but their fortunes definitely improved.