Lengyel was hired by athletic director Joe McMullen after head coach Rick Tolley was killed along with most of the Marshall coaches and players in the crash. When Lengyel arrived at Marshall he was forced to recruit athletes from other sports (baseball and basketball) as well as allow a large number of walk-ons in order to rebuild the devastated football program. Although the team struggled in Lengyel's first season at the helm, it managed to win a stunning 15–13 victory over Xavier, scoring a touchdown on the final play of the game. His overall record at Marshall as the head coach was 9–33.
After leaving Marshall, Lengyel went into the private sector before returning to sports as associate director of athletics at Louisville (1978–1980) and Missouri (1980–1983). He then went to Fresno State as director of athletics from 1983 to 1986. He returned to University of Missouri to become their athletic director from 1986 to 1988.
Lengyel also served many years on the Board of Trustees for the Foundation of the United States Naval Academy. He is currently the vice president of business development for XOS Digital, a sports media and technology company.
On January 12, 2008, seven members of a high school basketball team from Bathurst, New Brunswick, Canada and their coach's wife were killed in a highway crash when the 15-seat van they were traveling in collided with a tractor-trailer while returning from a game in Moncton in snowy conditions. Drawing similarities between the two tragedies, on March 13, 2008, Jack Lengyel funded his own traveling expenses to New Brunswick, Canada to assist in counseling the grieving community.
Lengyel went on record with the Canadian Press stating that schools should not be transporting students in small, multi-passenger vans. The New Brunswick government announced soon after the crash that it was suspending the use of the vans.