I do not think that one set to failure provides enough stimulus, both neural and time under tension to ensure a rugby player to get full benefit out of there training plan, although I do believe that you can make some good gains with it at certain times as a variation to training, as Louie say “everything works, but nothing works for ever” my first job in the fitness industry was an instructor at the Nautilus Fitness and Leisure Centre, in Crows Nest, Sydney, I trained exclusively using the principles, I got strong on the equipment but had some very bad shoulder injuries on the rugby field, that was from age 17 – 19,
after starting weight training at 15 in the traditional powerlifting/bodybuilding model, I returned to that style after the Nautilus experience, adding Olympic movements as well,I would never go back to just one set, cheers, ash