Spin numbers tell you almost nothing without depth

A heavily spun ball that lands short is a gift, and the broadcast graphic celebrating the revolutions will never mention it.

Broadcasters love an RPM figure. Big number on screen, commentator says something about how the ball is dipping viciously, everyone nods. It's the tennis equivalent of a speed gun reading, and it's about as informative.

Spin does one thing: it changes the ball's flight so you can hit harder without hitting long, and it makes the bounce jump. Both are useful. Neither means anything on its own, because the shot's actual value is set by where it lands and how high it sits when the opponent takes it.

Think about what heavy topspin does to trajectory. More spin means a steeper descent, which means the ball comes down earlier for a given swing speed. That's exactly why you can swing out. But it also means that if you don't swing hard enough, or if you brush too much and drive too little, the ball drops around the service line with a lovely arcing shape and a spin number that would look great on television. Your opponent steps in and takes it early on the rise. You've spun yourself into trouble.

The number that matters is the combination: depth first, then height at the bounce, then spin. A ball landing within a metre of the baseline pushes an opponent back regardless of how it's shaped. A ball landing there and kicking up to shoulder height on a one-handed backhand is close to unplayable. A ball landing short with the same revolutions is a mid-court sitter.

This has a coaching consequence that gets ignored constantly. When a junior's forehand starts landing short, the reflex is to tell them to hit through the ball more, flatten it out, get it deeper. Sometimes right. Often the problem is the contact point, not the swing shape. Late contact forces a brushing, upward path with no forward drive, and you get maximum spin with minimum depth. Fix the timing and the same swing produces a heavy deep ball.

The other thing worth saying is that spin has diminishing returns and a real cost. Past a certain point the extra revolutions buy you very little bounce height and demand a lot more racket-head speed, which comes out of your shoulder and your lower back over the course of a season.

So by all means enjoy the graphic. Just don't let anyone tell you a player is dominating because his forehand is spinning fast. Watch where it lands. That's the whole story.