Brett trained Boris Becker in 1989 when the German was superior and won both Wimbledon and the US Open.
During his career, he also coached Mats Wilander and Henrik Sundström and international stars such as Goran Ivanisevic and Maren Cicic.
Becker wrote in his biography that Brett was "tough, just what I needed".
"He made it clear to me that he expected willingness, discipline, willpower, punctuality.
Three hours of training in the morning, three hours in the afternoon.
"What you do afterwards does not interest me," Becker wrote.