Two key statistics that are required to fully understand match outcomes: the Forced Errors/Winners and Unforced Errors. Let’s review what they are and why they are crucial in understanding matches.

A Forced Error is a mistake attributed to the pressure created by the other player’s ball. This is different from the more familiar concept of the Unforced Error. An Unforced Error is a mistake that a player makes on an easy or routine ball—the error stems from the player’s inability to execute what should be a simple stroke or return.

A player generates a Forced Error through pace or location, or a combination of both. For example, a deep, high-velocity crosscourt forehand. The other player reaches the ball on the run and takes something resembling a normal swing, but is unable to control the ball and return it into the court. Even though the player had a chance to make a return, the error was “forced” by the opponent’s aggressive play.

Forced Errors are critical statistics because they account for up to half or more of the points in most matches.

The Aggressive Margin

So tracking Forced Errors is critical. Once we start to track Forced Errors, we can then combine them with the better-known stats of Winners and Unforced Errors to calculate the second key stat, what is called the Aggressive Margin.

The Aggressive Margin is the total of a player’s Winners and Forced Errors minus his Unforced Errors.

For example, let’s say a player hits 10 Winners and generates another 10 Forced Errors. That’s plus 20. Let’s say he makes 10 Unforced Errors, that’s minus 10. Subtract the Unforced Errors from the Winners and Forced Errors (20-10 = 10.). That’s an Aggressive Margin of +10.

The Aggressive Margin gives us an instant understanding of how a given match was really won or lost. The Aggressive Margin can be a positive or a negative number. It shows whether a player is playing positive tennis, or simply relying on his opponent to make more errors than he.

The Aggressive Margin is not an absolute; it’s a relative measure that reflects the quality of the points and shot-making between particular players at a particular level in a particular match.

This basic principle of positive percentage tennis seems to be virtually universal among successful players at all level. They understand their shot-making capabilities and use them to set up and execute winning point patterns.

Statistical tennis is the key to victory. The best players will win more points than they lose by playing correct patterns and making high percentage shot execution.

Developing the ability to win points through positive shot making is the key to winning—and making sure your positive shot-making exceeds your unforced errors.

Unless you can play positive statistical tennis on a consistent basis, your only hope is that your opponent has worse negative numbers than you. This explains why some players win one match, think they are playing great, and then are mystified when they play the same way against another opponent and lose badly.