nothing short of 7-8 hours of training and hitting against 2-4 different practice partners is going to get it done.
all heavy topspin players require immense amount of training. especially those that have won a lot in our sport:
1. vilas
2. borg
3. muster
4. clay warrior (rafa)
rafa was hitting 7-8 hours a day in 2008 in the what little off season tennis gave the players. he also played a lot. for instance he played and won more hard court matches than anyone on the planet.
his youth did the rest. now with the youth gone he is not doing nearly enough. I am afraid the decline in the game and fitness will continue at this current rate.