stan has the same problem every other single hander has on the tour in modern tennis in my estimation:
single hander has too many variables. it is not consistent enough for the modern game. roger did well with it because every other aspect of roger's game was world class. his serve was among the biggest in history for example. his forehand was one of the greatest ever. and so on.
you can do well here and there with a single hander and even have a great tournament but you cant consistently dominate with a single hander in modern tennis.
stan had a tournament of his lifetime in Melbourne and now its over. it will be very difficult to repeat that success and that type of performance.