CHICAGO — Johnny Bach, whose defensive expertise as an assistant to Phil Jackson helped the Chicago Bulls win three NBA titles from 1991 to 1993, has died. He was 91.

Bach was the head coach of the Golden State Warriors from 1983-86 before joining the Bulls as an assistant. He also worked as an assistant for Charlotte, Detroit and Washington. He returned to the Bulls in 2003 and retired in 2006 after more than a half-century in coaching.

“Johnny was a true treasure in the world of basketball,” Chicago executive vice president of basketball operations John Paxson said in a statement. “He was the classic ‘old school’ coach who came to work each and every day with energy and enthusiasm for the game he loved. His zest for life and basketball were unparalleled.”