Diebel's mother, who hoped for the best but was well aware of Nelson's behavioral issues, arranged for him to attend the
Peddie School in
Hightstown, New Jersey beginning in December, 1986, where the 16-year old would swim under talented first year Head Coach Chris Martin. Martin told Diebel he could use him on the swim team but he would have to do exactly what he was told, and if he was looking to fight, he could fight the rather large, strong, and imposing 6 foot 4 inch, 225 pound, Martin. Martin coached the Peddie School from 1986-1992, and in a few years succeeded in restoring the school's place as a national leader in swimming among private schools. He would coach at the University of Florida in 1992. Diebel and Martin eventually reached an understanding. Only six months after arriving at Peddie, Diebel won a national championship, and a year later made it to the finals of the 1988 Olympic trials in the 100 and 200 breaststroke. He performed well, but did not make the U.S. team. Six weeks after the trials, he slipped while diving from the Peddie stands into the pool, and landed on a balcony, breaking both wrists. He required hours of surgery, and several pins, but managed to recover. In pre-Olympic international competition, Diebel won silver medals in the 200 breaststroke at the 1989 Pan Pacifics and the 1991 Pan American Games. Training hard for the Olympics, in March 1992, he swam a 54.48 for the 100-meter freestyle, setting the American record, but adding stress to his body. While preparing for the 1992 trials during his Freshman year at Princeton, Diebel did less well absent the motivating force that his former coach Chris Martin had provided. He did not perform well at the 1991 Pan American games in Cuba. He began to suffer from chronic tendinitis in the rotator cuff and biceps tendon of his right shoulder, requiring him to reduce the intensity of training required to prepare for the Olympic trials. ==1992 Barcelona Olympic gold medals==