This begins as a cooperative and controlled drill which ends up into a competitive play.
The players are lined up in two one-up-one-back formations: player A at the baseline, his partner B at the net; player C at the baseline opposite from A, his partner D at the net (see graphic below).
Drill:
Player B has a basket of balls nearby to feed from. He begins the drill by feeding a courtesy ball to C who will have to send it cross-court to A who must hit it to D; the latter will tap (volley) the ball to B.
Once the 4 shot sequence is completed, the last player (B) will continue hitting the ball towards C and the point is played out from there on.
So what begins as a cooperative rally, it ends up in a play-to-win situation where players are allowed to move positions once the 4 shot rally is initiated.
Play first to win 4 points then players switch places clockwise.
If players like the drill, they can apply it having the net players on the deuce side and baseline ones holding the ad sides.
Note:
Recommended for intermediate and advanced players, this drill promotes strokes control and accuracy.