I believe it was famed Australian coach Harry Hopman — who tutored the likes of Roy Emerson, John Newcombe, Rod Laver, and others – who invented the Two-On-One Drills; which are some of my favorite workouts.
What you need… Three players of about equal ability, who are willing to “play the roles” of practice partners. That means feeding balls and not going for winners, when it is there turn to do that. Use at least 8 or 10 decent practice balls – that always start in the hands of the two “feeders.”
After warming up, the man alone (who is one being “drilled”) starts on the baseline, while his two “practice partners” are at the net (with all the balls). They try to always have a ball in their hands and feed him balls just far enough from where he is to make him move to hit a groundstroke. They feed and volley in a somewhat continuous activity as long as balls are available nearby (one practice partner can be picking up balls while the other is still feeding).
The baseliner can hit the ball wherever he wants: down the line, down the middle, etc. Do that for four, five, ten minutes – or till the baseliner is getting tired; then stop, pick up all the balls and rotate the next man to the baseline.
After all three have had their turn on the baseline, the first “practicer” now starts on the service line at the T near the net; while his two practice partners (with all the balls in hand/pocket) have moved to the baseline. They then start feeding and hitting hard groundstrokes at the net man, who can volley anywhere he wants.
The volley practicer should not just camp himself three feet from the net and hit put-away volleys; but should regularly back up to the T and start with the harder, longer volley. Again, do that till the practicer has had his fill and rotate rolls.
The practicer starts half way between the service line and the net (like he is in an aggressive net position) and his two partners are on the baseline. They feed him overheads. In this drill, you can keep score if you like: the net man can hit to the doubles alleys but the baseliners have to feed only to the singles. All overheads and first to seven wins.
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