Hours of Play/Training for Optimal Junior Development
My name is Mitch Bridge, and I have been coaching national-level juniors for over 20 years. If you are trying to train a future top level professional player, that player will need to be working on his game a minimum of 4 hours daily. The following areas of training need to be included in his/her regimen: one-on-one or two-on-one instruction, match or sets play, live ball training, strength training, speed and agility training, flexibility, massage/muscle work, serve/return, video/pro tennis viewing and analysis, and cardio training, with some relaxation exercises.
With this vast amount of potential training, it is easy to fill up available time to perfect your game. When you play less than 4 hours you have to skip too many of these variables to develop well enough to be a top player. This game is extremely demanding, and great players are completely entrenched in it. Also, using Federer, the most gifted player of all, is never a good measure for us humans.
Having said the above, every player has different demands on his/her time, and you need to do the best with the time and resources that you have. Some players can do a lot with 2 to 2 1/2 hours per day. With this schedule you can't take days off too often, and heavy monitored tournament play is a must.