Answer: Roger Friggin' Reid
OK, I don't want to undersell the players. Gary Trost was a very solid big man. Nixon and Heslop were great shooters. Russell Larson was one of the best freshman in BYU history. Having said that, you don't really look at that roster and think "25-7 record, regular season and conference tournament champs".
If college coaching was just the nuts and bolts: game planning, matchups, drawing up plays, maximizing talent, etc., then Roger would be one of the best coaches ever. In other areas, he had some weaknesses.