ferentz was the offensive line coach at the university of iowa under head coach hayden fry for nine seasons, from 1981 to 1989. eleven hawkeyes coached by ferentz went on to play in the national football league (nfl). three of them were first round picks in the nfl draft, and five of his players were first team all-big ten conference selections. six of those players played over 100 games in the nfl: og ron hallstrom, og mark bortz, ot brett miller, c joel hilgenberg, ot john alt, and og bob kratch. og mike haight played in 63 games as well.