Not looking at their pre-pro years, who benefited the most from their coaches over the years?
I'm leaning towardsw Djokovic over Nadal over Federer.
Federer seemed to be slow and stubborn to make changes. He did make them but they didn't really solve any of his problems vs. Nadal on clay nor give him the upper hand vs. Djoker later in his years. I feel a lot of his drive and style of play came from him more so than his coaches.
Toni Nadal was great for Rafa for years and the switch to Moya did seem to rejuvenate his career.
Djoker seemed to get a lot out of each of his coaches. A lot of support from Vajda, Becker brought him confidence and Goran seems to keep him on track too.