The body serve is the cheapest free point in tennis

Serving straight at a returner removes his swing room and demands no accuracy near a line, yet most players use it once a set.

Wide, or down the T. Those are the two serves everybody practises, and both of them require the ball to land within a foot or so of a line at high speed. Miss by that foot and it is a fault, and the player is now hitting a second serve.

The serve into the returner's hip requires none of that precision and it is used a fraction as often.

The reason it works is mechanical rather than psychological. A groundstroke needs space between the body and the ball. The returner has to create that space, and against a serve arriving at his front hip he can only do it by moving backwards, which he does not have time for, or by moving sideways, which forces a decision about which side to take the ball on. That decision is the whole point. He has under half a second and two options that both feel wrong. The result is a cramped return, usually short, usually down the middle, which is precisely what a server wants.

It is also the most forgiving serve in the book. The target is a person, roughly two feet across, standing in the middle of a nine foot box. There is a large margin on both sides, so a server can hit it near his top speed without the fault risk of a line serve.

The obvious objection is that the shot becomes readable if you use it constantly, and that is true of anything. But the current usage rate is nowhere near the point of diminishing returns. Most club players and plenty of professionals go entire sets without one, then wonder why a returner is standing comfortably and swinging freely at every ball.

There is a second use that gets overlooked. On a big point, when the server is tight, the body serve is the one that survives tension. A cramped arm on a wide serve pulls it into the net tape. A cramped arm aimed at a torso still lands in the box.

I would set a quota. One in five, minimum, mixed through both boxes and both service points. Then watch where the returner starts standing.

The moment he begins moving before the toss, you have already won something, and you have not hit a line all afternoon.