Some people stay too late in boxing. Others leave too soon. Oscar Suarez was one of the latter.

Last week boxing lost more than a good young trainer when the 47-year-old Suarez passed away quickly after being diagnosed with pancreatic cancer. It is the same despicable disease that took pro football union chief Gene Upshaw only days after he was diagnosed. It is also what claimed my father in short order, the only time in his life where pain seemed to overcome him in a way he could not hide from the rest of the world.

Pain was Oscar Suarez’s business. He inflicted it at times on his fighters, pushing them physically and mentally to prepare them to be the best they could be. But unlike too many of his peers he also protected his fighters from it when he could, shielding them both from beatings they did not deserve to take and from the mental anguish of having to surrender.

It is a difficult line a trainer walks between pushing his fighters to the brink without sending them over it. Boxing is, after all, the pain business but Suarez seemed to be one of those who understood there are limits.

What I remember most about him was not his greatest triumph in the corner of Acelino Freitas, the wonderfully pleasing Brazilian champion who won the lightweight and super featherweight titles with Suarez in his corner. Rather I recall most the night Suarez did the hardest thing a trainer has to do, which is to tell a brave fighter he has had enough.

In what would be the final fight of Freitas’ career, Suarez stepped into the ring and refused to allow him to take any more punishment from a young Juan Diaz. Suarez understood what Freitas’ angry supporters did not. His man was in an untenable position, fighting a fight he could not win but one that could leave him changed forever.

So he stepped in and defended his fighter when the fighter could no longer defend himself. He did the same thing three years earlier in the only other loss of Freitas’ career but this was a different circumstance. In this fight, Diego Corrales had dropped Freitas three times late in what had been a brutal fight, momentarily breaking Freitas’ spirit.

Freitas clearly elected not to go on even though some felt he was physically able to and thus had somehow been derelict in his duty. Suarez realized the situation and took responsibility for the stoppage, claiming he had told Freitas to quit.

He had not but in both cases Oscar Suarez had served his fighter well. He had stood up for him when he could not stand up for himself, which in some ways is a trainer’s first responsibility.

Suarez also worked with fighters like Naseem Hamed and Jhonny Gonzalez and did a good job with them. How great a trainer he might have become over the years the world will never know but that is really of little consequence today.

What is important is that the boxing world acknowledge it lost a good man, a compassionate man, a man who was an ambassador for his sport. His wife, Marie, has lost a husband. Their children have lost a father. And Popo Freitas has lost his great and good friend.

“I have lost a great friend,’’ Freitas said in a statement issued before he flew from Brazil to New Jersey to visit Suarez in his last days proving he had learned well Oscar Suarez’s greatest lesson. When it is toughest you stand by your man, win or lose. You stand there to the end, doing what you can to ease his pain.

That is what Oscar Suarez did so many times after fights. Long after the crowds were gone and all that was left were the bruises and pain only a fighter knows, he was with his man. With him to the end.