DL from day one. He was told that during recruiting and the plan for him from the instant he got to ND was to redshirt him. He was 6'6" and about 235 to 240. They wanted him up to 280 or more before playing him. He had to set his alarm twice per night to wake up and drink a shake with whatever mix of crap in it they wanted him to drink to gain weight.
He did in fact redshirt, but he left the team without ever playing a down mainly due to injury during the first Holtz winter workouts when he took over. He tore both hamstrings badly -- due to genius lifting techniques from the Faust era where he was exclusively doing squats and nothing to balance that out.
Anyway, I can say with 100% absolute certainty that ND was very overtly redshirting as of 1985 -- and since he was recruited in 1984 and told before he ever got to ND that it would be done, that means it was really happening at least since 1984.