Tennis statistics explained

What is an unforced error in tennis?

An unforced error is a mistake made with no pressure from the opponent. The player had the time, the balance and a normal shot to play, and missed it. The ball goes into the net, behind the baseline, or outside the sideline.

Below professional level it is the most common way a point ends. At the top of the game winners and unforced errors are close in number. In club tennis, errors decide many more points than winners do, which is why the count matters more than it looks.

Who decides if an error is forced or unforced?

A person does. The rules of tennis do not define an unforced error, and no official calls one. At a professional tournament a statistician watches the match and makes the call. Two statisticians can watch the same point and disagree.

The working rule is the position of the player. The player had time and stood in a normal position, so the error is unforced. The opponent pulled the player wide, or hit hard enough to take the time away, so the error is forced.

For your own match the label matters less than the method. Count the same way in every match. A trend across ten matches is useful. A number counted one way in March and another way in June is not.

What is a winner in tennis?

A winner is a shot the opponent does not touch. A serve the opponent does not touch is an ace, which is a winner from the serve.

A winner is not the same as a point won. Most points are won because the opponent missed. Counting winners alone makes a match look like a highlight film, and hides the errors that decided it.

The useful number is the two together: unforced errors for each winner. A ratio near 1 is aggressive and controlled. A ratio of 3 says the risk is not paying for itself.

What is a good first serve percentage?

first serves in ÷ first serve attempts

First serve percentage is the share of first serves that land in the correct service box. A player who hits 60 first serves and lands 36 has a first serve percentage of 60.

On the professional tour the number usually sits near 60 percent. That is the honest answer to "what is good", and it is also the least useful part of it.

A very high percentage is frequently a warning. It says the first serve is slow enough to be safe, so the opponent attacks it and the player wins fewer points behind it. Read the percentage together with the points won on the first serve. One number without the other can move in the wrong direction and look like progress.

What is break point conversion?

breaks converted ÷ break-point chances

A break point is a point that wins the game for the player who is receiving. Break point conversion is the share of those chances that become a break.

About 40 percent is common at professional level, so more than half of all break points are lost by the player who earned them. A low conversion in one match is normal. A low conversion across many matches is a pattern worth training.

Read the chances as well as the conversion. Four chances taken from six is a different match from four taken from twenty, and the second player has a returning problem rather than a nerve problem.

What is a down the line error, and why does it happen?

A player hits a sequence of shots in one direction, for example cross-court forehands, and then changes the direction of the ball down the line. The shot goes wide, long, or into the net. This is a change of direction error, or COD error.

The error belongs to the direction change and not to the shot type. The same forehand that was safe five times cross-court is the one that misses when it goes down the line, because the player must hit across the body and the margin over the net is smaller.

It is worth counting on its own. It shows where a player loses control at the moment the player tries to open the court, which is the moment a point is usually won or lost.

How do I count these statistics in my own match?

There are three ways, and they cost different amounts of attention.

A paper score sheet. Somebody watches and writes a mark for each point. It works, it is free, and it needs a person who is not playing and does not lose concentration.

A video and a pause button. You record the match and count afterwards. Nothing is missed, and an hour of tennis costs more than an hour of counting.

Automatic marking. Tencoline finds the shots in the video and labels them, and the match summary counts the winners, the unforced errors, the first serve percentage and the break points from those marks. You correct what is wrong instead of writing everything from the start.