A couple of years ago, while covering Saúl "Canelo" Álvarez's return to Guadalajara, I visited the gym where he began a brilliant two-decade career that made him the undisputed super middleweight champion and champion in four different divisions. There, Chepo Reynoso, the trainer who took him in at age 14, spoke to me about the inevitable expiration date of a boxer when I asked him how much longer we would have Álvarez as a professional fighter. Reynoso reminded me that Álvarez has been boxing since he was a child and that he was already a professional at 15. Because of his discipline and competitiveness, Álvarez became a multiple world champion and the Mexican athlete who has earned more money than any other boxer from his country. But all that effort eventually takes its toll. "When he sees that his body is no longer responding, even though he works hard and takes care of himself, it will be time to say goodbye. Your body tells you, 'Stop, I can't do this anymore,'" Reynoso, now 72, told me. He accompanied Álvarez in his painful loss to Terence Crawford Saturday in Las Vegas.