This is a drill that is always harder than it sounds. I always enjoyed the challenge of this drill. The purpose of this drill is to help you develop deeper groundstrokes.
This drill takes 2 people. The goal of this drill is to hit groundstrokes beyond the service line. Any groundstroke that lands before the service line you must stop and start completely over. The drill is simple, see how many balls you can keep in play. Set a number goal and try to beat it. Next time try a higher number. 20 is a good number to start with, that means you have to hit 10 groundstrokes and so does your partner. Start from there and see how many you can get to.
I used to play with a guy who would not let me leave the court until we did this drill and hit 50 in a row after our matches. It is tough, but very rewarding!!!